Source: http://www.google.com/patents/US7877540?ie=ISO-8859-1&dq=%235,519,867
Timestamp: 2015-03-03 07:54:05
Document Index: 535858247

Matched Legal Cases: ['arts 3', 'Application No. 60', 'application No. 06848548', 'application No. 06848548', 'art 4', 'art 4', 'Application No. 095146712']

Patent US7877540 - Logically-addressed file storage methods - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsFiles that are mapped to a logical address range by a host become logically fragmented prior to being sent to a memory system. Subsequently, the logically fragmented portions are reassembled when they are stored in blocks in the memory system. The host supplies information to the memory system regarding...http://www.google.com/patents/US7877540?utm_source=gb-gplus-sharePatent US7877540 - Logically-addressed file storage methodsAdvanced Patent SearchPublication numberUS7877540 B2Publication typeGrantApplication numberUS 11/302,764Publication dateJan 25, 2011Filing dateDec 13, 2005Priority dateDec 13, 2005Fee statusPaidAlso published asUS20070136555Publication number11302764, 302764, US 7877540 B2, US 7877540B2, US-B2-7877540, US7877540 B2, US7877540B2InventorsAlan Welsh SinclairOriginal AssigneeSandisk CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (108), Non-Patent Citations (24), Classifications (17), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetLogically-addressed file storage methods
US 7877540 B2Abstract
Files that are mapped to a logical address range by a host become logically fragmented prior to being sent to a memory system. Subsequently, the logically fragmented portions are reassembled when they are stored in blocks in the memory system. The host supplies information to the memory system regarding file-to-logical mapping of data prior to sending the data. The memory selects storage locations for the data based on the files to which the data belong.
1. A method of storing sectors of data from a plurality of files in a non-volatile memory array, sectors of each of the plurality of files mapped to a common logical address space by a host, comprising:
receiving file allocation information from the host that indicates a file to which a sector of host data is allocated;
subsequently receiving the sector of host data from the host for storage in the non-volatile memory array; and
subsequently storing the sector of host data in the non-volatile memory array in a physical location that is determined according to the file to which it is allocated according to the file allocation information from the host, such that the sector is stored in an erase block that is dedicated exclusively for storage of sectors from the file, the erase block storing sectors of the file having discontinuous logical address ranges.
2. The method of claim 1 wherein the file allocation information from the host includes a sector of File Allocation Table information.
3. The method of claim 2 wherein the sector of host data is in a cluster of sectors and the sector of File Allocation Table information includes a File Allocation Table entry pointing to the cluster.
4. The method of claim 1 wherein the file allocation information from the host includes a sector of directory information containing an entry for the file.
5. The method of claim 1 wherein subsequent to storing the sector of host data, additional information is received from the host indicating that the sector is the last sector in the file and in response the file is closed and scheduled for reclaim.
6. The method of claim 1 further comprising receiving two or more identical sectors of control data from the host and in response carrying out reclaim operations while providing a status indicator to the host.
7. The method of claim 1 further comprising receiving two or more identical sectors of control data and in response preparing the memory array for a loss of power.
8. A method of storing sectors of host data from a host file in a non-volatile memory array having a metablock as the minimum unit of erase, sectors from the host file and other files mapped to a common logical address space, comprising:
receiving a first plurality of sectors of data of the host file, the first plurality of sectors occupying a first portion of the logical address space;
subsequent to receiving the first plurality of sectors, receiving a second plurality of sectors that are not of the host file, the second plurality of sectors occupying a second portion of the logical address space;
subsequent to receiving the second plurality of sectors, receiving a third plurality of sectors of the host file, the third plurality of sectors occupying a third portion of the logical address space, the first portion of the logical address space and the third portion of the logical address space being logically discontinuous;
in response to information identifying the first and third portions of the logical address space as allocated to the host file, storing the first plurality of sectors and the third plurality of sectors in a first metablock of the memory array;
storing the second plurality of sectors in a second metablock of the memory array
wherein the first metablock is dedicated to storing data of the host file; and
wherein the information is received prior to receiving the first plurality of sectors of data of the host file.
9. The method of claim 8 wherein the first and third portions of the logical address space are identified as allocated to the host file by directory and File Allocation Table sectors sent by the host.
10. The method of claim 8 wherein the second portion of the logical address space extends from the first portion of the logical address space to the third portion of the logical address space, further comprising: prior to receiving the second plurality of sectors, receiving a directory sector indicating that a first cluster of the second plurality of sectors is not allocated to the host file.
11. The method of claim 10 further comprising: prior to receiving the third plurality of sectors, receiving a File Allocation Table sector indicating that a first cluster of the third plurality of sectors is allocated to the host file.
12. A method of storing a host data file in a non-volatile memory array that has a metablock as the minimum unit of erase, comprising:
receiving file allocation information regarding a first plurality of sectors of a host data file prior to receipt of any sectors of the host data file, the file allocation information identifying the sectors of the first plurality of sectors as belonging to the host data file;
subsequently receiving the first plurality of sectors of data of the host data file, each of the first plurality of sectors having a logical address from a logical address space defined for the memory array, the first plurality of sectors having logical addresses that occupy two or more discontinuous portions of the logical address space;
receiving a second plurality of sectors of data that are not of the host data file, each of the second plurality of sectors having a logical address from the logical address space, the second plurality of sectors received interspersed with the receipt of the first plurality of sectors;
in response to determining that the two or more discontinuous portions of the logical address space are occupied by data of the host data file, storing the data from the two or more discontinuous portions of the logical address space in a metablock that contains only data of the host data file.
13. The method of claim 12 wherein the file allocation information is in the form of File Allocation Table and directory sectors.
14. The method of claim 12 further comprising receiving end of file information indicating the logical address of the end of the host data file and in response closing the host data file and scheduling the host data file for garbage collection.
15. A method of interfacing a memory system with a host that allocates sectors of host data files to a common logical address space, comprising:
the memory system receiving a plurality of sectors of host data from the host, the plurality of sectors allocated to a host file, the plurality of sectors of host data having logical addresses assigned by the host that are not contiguous; and
the memory system determining whether the plurality of sectors are allocated to the host file and, in response to determining that the plurality of sectors are allocated to the host file, the memory system storing the plurality of sectors in an erase block that stores only data of the host file; and
wherein the memory system determines whether ones of the plurality of sectors are allocated to the host file using file allocation information received from the host prior to receipt of the plurality of sectors of host data from the host.
16. The method of claim 15 wherein the file allocation information that is received from the host includes one or more File Allocation Table sectors.
17. The method of claim 15 wherein the file allocation information that is received from the host includes one or more directory sectors.
18. The method of claim 15 wherein the memory system further determines that the end of the host file has been received and in response closes the file and schedules the file for garbage collection.
This application is related to U.S. patent application Ser. No. 11/300,568, entitled, �Logically-Addressed File Storage Systems,� filed on the same day as the present application.
This application relates to the operation of re-programmable non-volatile memory systems such as semiconductor flash memory, and, more specifically, to the management of data within such a memory. All patents, patent applications, articles and other publications, documents and things referenced herein are hereby incorporated herein by this reference in their entirety for all purposes.
A common prior interface between a host and a memory system uses a logical addressing scheme for sectors of data stored by the memory. However, host files often become logically fragmented when they are mapped to a logical address space and as a result they may be distributed widely throughout the memory array. This can make managing the memory array more difficult because blocks in the memory array contain portions of many files and therefore often contain a mix of valid and obsolete data. In order to reclaim the space occupied by obsolete data, it may be necessary to copy a large amount of valid data.
A memory system according to an embodiment of the present invention receives data from a host that uses a logical addressing scheme. The host first maps host files to a logical address space. Then, the host provides the memory system with signals that indicate which file a particular sector of host data is allocated to. Subsequently, when the sector of host data is received by the memory system, the memory system uses the allocation information that it previously received to determine where to store the sector of host data. Specifically, the memory system puts sectors from the same host file in the same metablock of the memory array. A file may occupy more than one metablock in this way. The host also signals when the end of a host file has been sent so that the memory system may close the file and perform operations to more efficiently store the file.
A notification scheme used by a host to inform a memory system of the allocation of sectors of data uses Directory and FAT sectors so that the signals of the notification scheme are compatible with prior logical interfaces. In particular, the start of a new file is identified by a Directory sector that indicates the first cluster of the file. Then, when the sectors of that cluster are sent, they are stored in a new metablock. Any cluster that is logically sequential to the previous cluster received may be presumed to be from the same file as the previous cluster. When a new cluster is sent by a host that is not from the same file as the previous cluster, the host indicates this change. If the new cluster is from a new host file (no sectors from this file previously sent, therefore no metablock open for the file) the host sends a Directory sector to indicate the start of a new file. If the new cluster is from an open file (sectors from this file previously sent and stored in one or more metablocks for the file), then the host sends a FAT sector including a FAT entry for the previous cluster of the open file including a pointer to the new cluster. In addition to sending signals to indicate file allocation information, the host may send a FAT sector to indicate the end of a file. Such a FAT sector contains an entry for the last cluster of the file indicating an End of File. Unlike prior schemes that store FAT and Directory information in nonvolatile memory, the present scheme sends the allocation information before sending the host data to which it refers. Also, most prior schemes do not provide for the memory system to use allocation information sent by the host as FAT and Directory sectors.
A memory system may use file allocation information provided by the host to keep data of a particular host file together. Even though the host file may be logically fragmented when it is mapped by the host to a logical address range, the memory system can use the information regarding this mapping to store data of a file in a dedicated block. Thus, a new block is opened when the host indicates the start of a new file. Subsequently, any data indicated as being from that block is stored in the same metablock. Additional metablocks are opened for the file as necessary. Eventually, the host indicates the end of the file, or the memory system closes the file for some other reason. At this point, if there is a metablock that is only partially filled with data from the host file, that residual data may be combined with similar residual data from other files in a common block. Subsequently, if the host deletes the file (as indicated by a Directory sector or otherwise) the space occupied by the file may easily be recovered with very little copying of valid data because most of the file is in dedicated metablocks. A notification scheme may also allow a host to inform a memory system when power is about to be removed so that the memory system can prepare for power loss (e.g. by storing any data in volatile memory to nonvolatile memory). A notification scheme may also allow a host to inform a memory system when power will be maintained so that the memory system can perform housekeeping operations such as reclaim operations.
FIG. 7 illustrates a common logical address interface between a host and a reprogrammable memory system;
FIG. 8 illustrates a file interface between a host and a reprogrammable memory system;
FIG. 9 illustrates a logical address interface used with logical address-to logical file conversion by a memory system;
FIG. 10 illustrates a logical interface between a host and a memory system with logical-to-physical address translation in the memory system being dependent on file-to-logical address information received from the host;
FIG. 11 illustrates the logical interface of FIG. 10 with a file logically fragmented by a host and subsequently defragmented by the memory system when it is stored;
FIG. 12 illustrates the storage of file allocation information for files A and B in a memory system using a Directory and File Allocation Table (FAT);
FIG. 13 illustrates operation of a notification scheme for host file A sent as logically sequential clusters of host data;
FIG. 14 illustrates operation of a notification scheme for host file B sent as clusters of host data including a jump in logical address;
FIG. 15A illustrates the storage of file allocation information for files C and D in a memory system including a Directory and File Allocation Table (FAT);
FIG. 15B illustrates a notification scheme for host files C and D that are sent as logically sequential clusters that alternate between clusters of sectors of file C and file D.
Flash Memory General Description
A current flash memory system and a typical operation with host devices are described with respect to FIGS. 1-7. It is in such a system that the various aspects of the present invention may be implemented. A host system 1 of FIG. 1 stores data into and retrieves data from a flash memory 2. Although the flash memory can be embedded within the host, the memory 2 is illustrated to be in the more popular form of a card that is removably connected to the host through mating parts 3 and 4 of a mechanical and electrical connector. There are currently many different flash memory cards that are commercially available, examples being the CompactFlash (CF), the MultiMediaCard (MMC), Secure Digital (SD), miniSD, Memory Stick, SmartMedia and TransFlash cards. Although each of these cards has a unique mechanical and/or electrical interface according to its standardized specifications, the flash memory included in each is very similar. These cards are all available from SanDisk Corporation, assignee of the present application. SanDisk also provides a line of flash drives under its Cruzer trademark, which are hand held memory systems in small packages that have a Universal Serial Bus (USB) plug for connecting with a host by plugging into the host's USB receptacle. Each of these memory cards and flash drives includes controllers that interface with the host and control operation of the flash memory within them.
As the parallelism of memories increases, data storage capacity of the metablock increases and the size of the data page and metapage also increase as a result. The data page may then contain more than two sectors of data. With two sectors in a data page, and two data pages per metapage, there are four sectors in a metapage. Each metapage thus stores 2048 bytes of data. This is a high degree of parallelism, and can be increased even further as the number of memory cells in the rows is increased. For this reason, the width of flash memories is being extended in order to increase the amount of data in a page and a metapage. While many examples described in the present application use metablocks and metapages as the units of erase and programming respectively, most of the techniques described are equally applicable where blocks and pages are the units of erase and programming. Similarly, techniques applied to memory systems using blocks and pages are generally applicable to metablocks and metapages.
Memory systems, especially memory systems embodied in removable cards, may communicate with different hosts via a standard interface. Different hosts may use different interfaces for communication with memory systems. Two categories of interfaces are those using a logical addressing system with a common logical address space and those using a file based addressing system.
A common logical interface between the host and the memory system is illustrated in FIG. 7. A continuous logical address space 161 is large enough to provide addresses for all the data that may be stored in the memory system. The host address space is typically divided into increments of clusters of data. Each cluster may be designed in a given host system to contain a number of sectors of data, somewhere between 4 and 64 sectors being typical. A standard sector contains 512 bytes of data and some overhead data.
When a File 2 is later created by the host, the host similarly assigns two different ranges of contiguous addresses within the logical address space 161, as shown in FIG. 7. A file need not be assigned contiguous logical addresses but rather can be fragments of addresses in between address ranges already allocated to other files. This example then shows that yet another File 3 created by the host is allocated other portions of the host address space not previously allocated to the Files 1 and 2 and other data. File 1, File 2 and File 3 are all assigned to portions of a common logical address space (logical address space 161) in this example.
The host keeps track of the memory logical address space by maintaining a File Allocation Table (FAT) and a Directory, where the logical addresses the host assigns to the various host files are maintained. The Directory and FAT are typically stored in the non-volatile memory, as well as in a host memory, and are frequently updated by the host as new files are stored, other files deleted, files modified and the like. When a host file is deleted, for example, the host may deallocate the logical addresses previously allocated to the deleted file by updating the Directory and FAT table to show that they are now available for use with other data files. In some cases, only the directory is updated when a file is deleted and FAT entries remain for obsolete clusters of data. A logical address used in the FAT may be referred to as a Logical Block Address (LBA), so an interface using such logical addressing over a logical address space that is commonly used for data from different files may be referred to as an LBA interface.
The memory system controller is programmed to store data files within the blocks and metablocks of a memory array 165 in a manner to maintain the performance of the system at a high level. Four planes or sub-arrays are used in this illustration. Data are preferably programmed and read with the maximum degree of parallelism that the system allows, across an entire metablock formed of a block from each of the planes. At least one metablock 167 is usually allocated as a reserved block for storing operating firmware and data used by the memory controller. Another metablock 169, or multiple metablocks, may be allocated for storage of host operating software, the host FAT table and the like. Most of the physical storage space remains for the storage of data files. The memory controller does not generally know, however, how the data received have been allocated by the host among its various file objects. All the memory controller typically knows from interacting with the host is that data written by the host to specific logical addresses are stored in corresponding physical addresses as maintained by the controller's logical-to-physical address table 163.
Data stored at specific host logical addresses are frequently overwritten by new data as the original stored data become obsolete. The memory system controller, in response, writes the new data in an erased block and then changes the logical-to-physical address table for those logical addresses to identify the new physical block to which the data at those logical addresses are stored. The blocks containing the original data at those logical addresses are then erased and made available for the storage of new data. Such erasure often must take place before a current data write operation may be completed if there is not enough storage capacity in the pre-erased blocks from the erase block pool at the start of writing. This can adversely impact the system data programming speed. The memory controller typically learns that data at a given logical address have been rendered obsolete by the host only when the host writes new data to their same logical address. Many blocks of the memory can therefore be storing such invalid data for a time.
Data consolidation and garbage collection take time and can affect the performance of the memory system, particularly if data consolidation or garbage collection needs to take place before a command from the host can be executed. Such operations are normally scheduled by the memory system controller to take place in the background as much as possible but the need to perform these operations can cause the controller to have to give the host a busy status indicator until such an operation is completed. An example of where execution of a host command can be delayed is where there are not enough pre-erased metablocks in the erased block pool to store all the data that the host wants to write into the memory and data consolidation or garbage collection is needed first to clear one or more metablocks of valid data, which can then be erased. Attention has therefore been directed to managing control of the memory in order to minimize such disruptions. Many such techniques are described in the following U.S. patent application Ser. No. 10/749,831, filed Dec. 30, 2003, entitled �Management of Non-Volatile Memory Systems Having Large Erase Blocks�; Ser. No. 10/750,155, filed Dec. 30, 2003, entitled �Non-Volatile Memory and Method with Block Management System�; Ser. No. 10/917,888, filed Aug. 13, 2004, entitled �Non-Volatile Memory and Method with Memory Planes Alignment�; Ser. No. 10/917,867, filed Aug. 13, 2004; Ser. No. 10/917,889, filed Aug. 13, 2004, entitled �Non-Volatile Memory and Method with Phased Program Failure Handling�; and Ser. No. 10/917,725, filed Aug. 13, 2004, entitled �Non-Volatile Memory and Method with Control Data Management.�
One challenge to efficiently control operation of memory arrays with very large erase blocks is to match and align the number of data sectors being stored during a given write operation with the capacity and boundaries of blocks of memory. One approach is to configure a metablock used to store new data from the host with less than a maximum number of blocks, as necessary to store a quantity of data less than an amount that fills an entire metablock. The use of adaptive metablocks is described in U.S. patent application Ser. No. 10/749,189, filed Dec. 30, 2003, entitled �Adaptive Metablocks.� The fitting of boundaries between blocks of data and physical boundaries between metablocks is described in patent application Ser. No. 10/841,118, filed May 7, 2004, and Ser. No. 11/016,271, filed Dec. 16, 2004, entitled �Data Run Programming.�
The memory controller may also use data from the FAT table, which is stored by the host in the non-volatile memory, to more efficiently operate the memory system. One such use is to learn when data has been identified by the host to be obsolete by deallocating their logical addresses. Knowing this allows the memory controller to schedule erasure of the blocks containing such invalid data before it would normally learn of it by the host writing new data to those logical addresses. This is described in U.S. patent application Ser. No. 10/897,049, filed Jul. 21, 2004, entitled �Method and Apparatus for Maintaining Data on Non-Volatile Memory Systems.� Other techniques include monitoring host patterns of writing new data to the memory in order to deduce whether a given write operation is a single file, or, if multiple files, where the boundaries between the files lie. U.S. patent application Ser. No. 11/022,369, filed Dec. 23, 2004, entitled �FAT Analysis for Optimized Sequential Cluster Management,� describes the use of techniques of this type.
To operate the memory system efficiently, it is desirable for the controller to know as much about the logical addresses assigned by the host to data of its individual files as it can. But it is difficult for the memory controller to know much about the host data file structure when the host/memory interface includes the logical address space 161 (FIG. 7), as described above.
File-Based Addressing
An alternative interface between a host and memory system for the storage of mass amounts of data eliminates use of the logical address space. The host instead logically addresses each file by a unique file ID (or other unique reference) and offset addresses of units of data (such as bytes) within the file. This file address is given directly to the memory system controller, which then keeps its own table of where the data of each host file are physically stored. This new interface can be implemented with the same memory system as described above with respect to FIGS. 2-6. The primary difference with what is described above is the manner in which that memory system communicates with a host system.
This file-based interface is illustrated in FIG. 8, which should be compared with the logical address interface of FIG. 7. An identification of each of the Files 1, 2 and 3 and offsets of data within the files of FIG. 8 are passed directly to the memory controller. This logical address information is then translated by a memory controller function 173 into physical addresses of metablocks and metapages of the memory 165.
Since the memory system knows the locations of data making up each file, these data may be erased soon after a host deletes the file. This is not generally the case for a typical logical address interface. Further, by identifying host data by file objects instead of using logical addresses, the memory system controller can store the data in a manner that reduces the need for frequent data consolidation and collection. The frequency of data copy operations and the amount of data copied are thus significantly reduced, thereby increasing the data programming and reading performance of the memory system.
Examples of file-based interfaces include those using direct data file storage. Direct data file storage memory systems are described in pending U.S. patent application Ser. Nos. 11/060,174, 11/060,248 and 11/060,249, all filed on Feb. 16, 2005 naming either Alan W. Sinclair alone or with Peter J. Smith, and Provisional Application No. 60/705,388 filed by Alan W. Sinclair and Barry Wright, and entitled �Direct Data File Storage in Flash Memories� (hereinafter collectively referenced as the �Direct Data File Storage Applications�).
Since the direct data file interface of these Direct Data File Storage Applications, as illustrated by FIG. 8, is simpler than the logical address space interface described above, as illustrated by FIG. 7, and allows the memory system to perform better, the direct data file storage is preferred for many applications. But host systems are primarily configured at the present time to operate with the logical address space interface, so a memory system with a direct data file interface is not compatible with most hosts. It is therefore desirable to provide the memory system with the ability to operate with either interface.
Logical to Virtual File Mapping
U.S. patent application Ser. No. 11/196,869, filed on Aug. 3, 2005, entitled �Interfacing systems operating through a logical address space and on a direct data file basis� describes systems that enable a memory system to interface with hosts using either a logically addressed interface or a file-based interface. FIG. 9 illustrates such a system. This example combines the host operation of FIG. 7 with the file based memory operation of FIG. 8 plus an added address conversion 172 within the memory system. The address conversion 172 maps groups of logical addresses across the memory space 161 into individual logical files a-j shown across the modified address space 161′. The entire logical address space 161 is preferably divided into these logical files, so the number of logical files depends upon the size of the logical address space and of the individual logical files. Each of the logical files contains data of a group of contiguous logical addresses across the space 161. The amount of data within each of the logical files is preferably made to be the same, and that amount equal to the data storage capacity of one metablock in the memory 165. Unequal sizes of the logical files and/or sizes different from the storage capacity of a block or metablock of the memory are certainly possible but not preferred.
Data within each of the individual files a-j are represented by logical offset addresses within the files. The file identifier and data offsets of the logical files are converted at 173 into physical addresses within the memory 165. The logical files a-j are stored directly in the memory 165 by the same processes and protocols described in the Direct Data File Storage Applications. The process is the same as that used to store data files 1-3 of FIG. 9 in the memory 165, except that the known amount of data in each logical file can make this easier, especially if that amount is equal to the capacity of a block or metablock of the memory. It is shown in FIG. 9 that each of the logical files a-j is mapped to a different one of the metablocks of the memory 165. It is also desirable that the file based data storage interact with the host in the same or an equivalent manner as present logical address memory systems with which the host has been designed to interface. By mapping individual logical files into corresponding individual memory metablocks, essentially the same performance and timing characteristics are achieved with the direct data file interface memory system as when a logical address space interface is used.
The data file based backend storage system of FIG. 9, designed to work through a traditional logical address space interface with a host, can also have a direct data file interface added. Both host data files from the file interface and logical files converted by from the logical interface are translated into memory metablock addresses. The data are then stored in those addresses of the memory by executing a direct data file protocol. This protocol includes the direct data file storage techniques of the Direct Data File Storage Applications previously listed.
Logically-Addressed File Storage
As described above, there are advantages to maintaining data in a memory system as files that are stored in contiguous areas of a memory array and are managed in a file-based manner. However, many hosts provide data to memory systems in the form of sectors of data with logical addresses. Host files may be logically fragmented in such a system so that a host file occupies multiple logical address ranges with other data occupying intervening logical address ranges. While mapping logical address space to virtual files in a predefined manner allows logically addressed data to be handled by a file based backend, virtual files retain the logically fragmented pattern of the logical address space so that a metablock that contains a single virtual file may contain data from many host files. It is desirable for a memory system to accept logically addressed data from a host and store it in a manner that keeps data from a single host file together in one or more blocks that do not contain data from many or any other files. In this way, some of the advantages of file-based storage may be realized even with a host that sends data in the form of sectors having logical addresses from a logical address space that is common to all files.
In one embodiment, a host sends information regarding a sector of data to a memory system prior to sending the sector of data. This information may be used by the memory system to store the sector with other sectors of the same file. In this way, sectors from the same file are kept together in particular blocks that may be dedicated to storing only that file (though some blocks may store data from more than one file). The information sent by the host may be in the form of FAT and directory sectors that give allocation information on the sectors that are about to be sent. This is in reverse order to the usual sequence where a host sends sectors of data and subsequently sends allocation information in the form of FAT and directory sectors. Also, in prior systems, the memory system does not generally use the contents of FAT and directory sectors to modify its operations.
One aim of a logically-addressed file storage scheme is to accept logically fragmented data from a host and store the file in a physical arrangement that is less fragmented than the logical arrangement. Thus, a file that is mapped to two or more portions of logical address space that are not contiguous (there are other logical addresses between the two portions) is stored contiguously in the physical memory array. Storing the file in a physically contiguous manner may mean that all the data of a file is stored in a single block, or when the data in the file exceeds the capacity of a block, one or more blocks are occupied exclusively by data from the file and only one block contains data from the file and other data that are not from the file. The blocks that store data from the file need not be in any particular arrangement. Thus, �contiguous� in this context does not mean that the blocks containing the file are located together but refers to the arrangement of data within individual blocks.
FIG. 10 shows a logically-addressed file storage scheme according to an embodiment of the present invention. File 1, file 2 and file 3 are sent by a host for storage in memory array 180. File-to-logical address conversion 160 is performed by the host in a similar manner to that shown in FIG. 7 so that files 1, 2 and 3 are mapped to a common logical address space 161. Files may become logically fragmented by this mapping as shown by data file 2 which occupies two portions of logical address space 161 that are separated by an intermediate portion that is not occupied by data of file 2. Similarly, data file 3 is split into two portions. In some memory systems, files may become much more fragmented with files occupying many separated portions of logical address space. File-to-logical address conversion information 182 is generated when data files 1, 2 and 3 are mapped to logical address space by file-to-logical address conversion 160. File-to-logical address conversion information 182 is passed to the memory. However, unlike many prior systems, in this case file-to-logical conversion information 182 is sent to the memory before the data that it refers to. Thus, information reflecting the mapping of file 2 to two different logical address ranges of logical address space 161 is sent to the memory before the sectors of data of those logical address ranges are sent. File-to-logical address conversion information 182 allows logical-to physical address translation 184 to be done in a way that uses file-to-logical address conversion information 182 to determine the physical locations where individual sectors are stored.
FIG. 10 shows metablock 167 allocated as a reserved block; metablock 169 allocated for storage of host operating software, the host FAT table and the like; and metablock 171 maintained in an erased block pool as before. FIG. 10 also shows File 1 stored in one metablock, File 2 in another metablock and File 3 occupying two other metablocks. Even though File 2 is mapped to two separate portions of logical address space 161, the two portions of File 2 are stored together as a result of the logical to physical address translation 184. Similarly, File 3 is logically fragmented into two parts occupying two portions of logical address space 161 that are separated from each other. Additional data that are not part of File 3 are mapped to the intervening portion of logical address space. However, the logically separated portions of File 3 are stored together in two metablocks that do not contain data of other files. This arrangement of files in metablocks that only contain data of a single file is advantageous because, when a file becomes obsolete an entire metablock becomes obsolete and there is no need for copying of valid data as is generally done during garbage collection. It may not be efficient to have all metablocks storing only data of one file because files may not fill an integer number of metablocks and maintaining unused portions of metablocks reduce memory capacity. However, fragmentation of files in the memory array may still be reduced compared with prior systems even where some metablocks contain data from more than one file
FIG. 11 shows an example of File A that is mapped to logical address space 161 and is logically fragmented into four portions by this mapping. File-to-logical address conversion information 182 regarding this mapping is sent to the memory before the data are sent to the memory. Thus, the logical addresses to which portions of File A are mapped are identified with File A by file-to-logical address information 182. Then, when the data of File A are sent to the memory, the locations at which the data of File A are stored are determined by their identification with File A. FIG. 11 shows the logical to physical translation 184 that takes place in the memory. The portions of File A that are mapped to separated portions of logical address space 161 are mapped to contiguous portions of physical memory array 180. In this example, metablock 4 is filled with data from File A and metablock 7 is partially filled with data from File A. The data in metablock 7 may later be combined with data from other files so that space in the memory array is not wasted. However, metablock 4 remains dedicated to storing only data from File A. Once File A is closed, the memory may consolidate the data in metablock 7 with other similar data from other files. A scheme for carrying out such consolidation of partial metablocks is given in the Direct Data File applications where residual file data from multiple files are combined in a single common block in an efficient manner.
Various notification schemes are possible to send file-to-logical address conversion information from the host to the memory. In one example, the notification scheme used follows the same format as generally used when storing control information in the memory. This scheme uses FAT sectors and directory sectors to update FAT and directory information in the nonvolatile memory so that it is available for later recovery. FIG. 12 shows how file allocation information may be stored. Files A and B are stored in a memory. A directory contains entries for both file A and file B. A directory entry contains various information about a file including the address of the first cluster of the file. Thus, for file A the directory entry indicates that cluster 2 is the first cluster, so the first FAT entry for file A is the entry for cluster 2. For file B, the directory entry indicates that the first cluster is cluster 0. The FAT contains cluster entries that indicate the next cluster for that file. Thus, when the location of the first FAT entry for a file is obtained from the directory, subsequent FAT entries are indicated by the FAT entry for the previous cluster allocated to that file. FAT entries may be considered to be �chained� because of the way one FAT entry points to the location of the next FAT entry for a particular file. For File A, cluster 2 is indicated by the directory as the first cluster. The entry for cluster 2 indicates that cluster 3 is the next cluster for File A. The entry for cluster 3 indicates that cluster 4 is the next cluster for File A. The entry for cluster 4 indicates an End of File (EoF). Thus, cluster 4 is the last cluster allocated to File A. For File B, the directory indicates that cluster 0 is the first cluster. The entry for cluster 0 indicates that cluster 1 is the next cluster for File B. The entry for cluster 1 indicates that cluster 5 is the next cluster for File B. The entry for cluster 5 indicates that cluster 6 is the next cluster for File B and the entry for cluster 6 indicates an End of File. Thus, cluster 6 is the last cluster of File B. FAT and directory information is generally maintained by a host and is stored in the nonvolatile memory on a regular basis by sending FAT sectors and directory sectors.
Previous schemes have used Directory and FAT structures to store file-to-logical address information. However, unlike previous schemes, a scheme according to an embodiment of the present invention sends file-to-logical address information before the data are sent to the memory. In a typical prior system, FAT and directory sectors were only sent after the data to which they referred were sent and stored in the memory. One reason to delay sending FAT and directory sectors is to avoid having incorrect information recorded in nonvolatile memory in case of a loss of power before the data was written. In one embodiment, a scheme avoids this problem by only writing part of the FAT for a file prior to storing the file to which it refers. In this way, if a loss of power occurs the partial FAT indicates that writing the file was not completed and that the file data may not be usable.
In an exemplary notification scheme, FAT and directory sectors are sent by the host to inform the memory about the file allocation of sectors of data that are to be sent by the host. It is not generally necessary to send file allocation information for each cluster of host data sent. In general, where a host sends sequential clusters of sectors, the memory assumes that the clusters belong to the same file. Thus, where a single file is sent as a stream of sequential clusters, the host may just identify the file before the first cluster is sent and send an end of file indicator after the last sector. FIG. 13 shows an example of the host sending File A of FIG. 12 to the memory. First, a directory sector 301 is sent indicating that cluster 2 is the first cluster of File A. Then the sectors of cluster 2 are sent and are stored by the memory in a new block 302 of the memory array because this is the start of a new host file. Subsequently, sectors of clusters 3 and 4 are received sequentially and are stored in the same block with sectors of cluster 2. After cluster 4 is received, the host sends a FAT sector 303 with an End of File entry for cluster 4 indicating that it is the last cluster in file A. Full FAT information for file A may also be sent at this point because the whole of file A has been stored. At this point, the memory can close file A and could perform reclaim operations if desired. This shows an example of a file that is sent in a logically sequential manner and without any intermediate writing to other files.
FIG. 14 shows the example of a host sending File B of FIG. 12. First, a directory sector 410 is sent indicating that the first cluster of File B is cluster 0. Then, the sectors of cluster 0 are sent and stored in a new block 412 because these are the first sectors of a new file. Then, the sectors of cluster 1 are received and because these are sequential to the sectors of cluster 0, it is assumed that they are also from File B, so they are also stored in block 412. Next, a FAT sector 414 is received that contains a FAT entry for cluster 1 and the pointer for this entry indicates that cluster 5 is the next cluster in file B. FAT sector 414 may not contain an entry for cluster 5 at this point because cluster 5 has not yet been sent by the host. FAT sector 414 informs the memory controller that although there is a jump in logical address from cluster 1 to cluster 5, the sectors of cluster 5 contain the next data from File B after cluster 1. Then, when the sectors of cluster 5 are received, they are stored with the sectors of cluster 1 in block 412. Then, cluster 6 is received and is also stored in block 412 because it is sequential to cluster 5. Subsequently, a FAT sector 416 is received that contains an End of File entry for cluster 6. File B can then be closed and reclaim operations can be performed if necessary on the block containing File B. In some cases, the memory may assume that when there is a jump in logical address that the host will continue writing the next cluster of the same file. In such a memory system, no specific notification is needed when the host continues writing data from the same file with a jump in logical address. FIG. 14 may be considered an example of a logically non-sequential writing of a file without intermediate writing to other files because, though there is a jump in logical address between sectors of cluster 1 and sectors of cluster 5, the host sends File B over a time period that is dedicated to sending File B (i.e. no sectors of data from other files are sent in this time).
FIG. 15A shows two files C and D mapped by a host to part of a logical address space. In this case, two files C and D are not only fragmented in logical address space but are also sent in a temporally fragmented manner. The clusters of files C and D are sent by the host in logical order so that cluster 10 is sent first, then cluster 11, then cluster 12 and so on. This involves some changes from one file to another even though the clusters are sent in logically sequential order. The memory is informed of these changes between files by the host.
FIG. 15B shows how the host informs the memory when the host starts writing to a different file. First, a directory sector 520 is sent indicating that cluster 10 is the first cluster of file C. Then, the sectors of cluster 10 are sent by the host and are stored in the memory array in a new block 522 because they are the first sectors of a new file. Next, the host sends another directory sector 524 indicating that cluster 11 is the first cluster of file D. Subsequently, cluster 11 is send and is stored in another new block 526. Then, cluster 12 is received and is stored with cluster 11 in block 526. The memory system assumes that, because cluster 12 is sequential to cluster 11 and the host has not indicated otherwise, that cluster 12 belongs to the same file as cluster 11. Next, a FAT sector is sent by the host with an entry for cluster 10. The entry for cluster 10 includes a pointer to the next cluster for the file of cluster 10 (file C). In this case the pointer indicates that the next cluster of file C is cluster 13. Then, when cluster 13 is received, even though it is logically sequential to the last cluster received (cluster 12) the memory system knows that cluster 13 is allocated to file C and so the sectors of cluster 13 are stored in block 522 with the sectors of cluster 10.
The following table summarizes the notification scheme for identifying file allocation of data of the above examples.
Host sends directory sector indicating first
cluster of new file
Host sends new FAT sector with entry for last
cluster of file pointing to next cluster
cluster of file pointing to next cluster OR
In addition to the above signals indicating the file to which a cluster is allocated, the host may send an indication that a cluster is the last cluster of a particular file by a FAT sector including an End of File entry for the cluster. This allows the file to be closed and allows the memory system to carry out reclaim operations on the blocks containing the file as described below.
In one example, when a file is closed by a host, the metablocks containing the file data are then marked as ready for reclaim operations. The techniques used to reclaim memory space in a memory system using techniques of the present invention are similar to those described in the Direct Data File Storage applications. In particular, when a file is closed there may be one or more metablocks that are full of data from the file but there is usually one metablock that is only partially filled with data from the file. In order to more efficiently store these residual file data the host may copy residual file data from one file to a metablock that contains residual file data from another file. Which residual file data are moved and the destination to which they are moved are chosen to keep the amount of unused memory space small. Thus, if a file is closed leaving residual file data occupying 30% of a metablock, the memory system will look for a metablock containing residual file data occupying 70% (or nearly 70%) of a metablock. A metablock containing portions of data from more than one file may be considered a common block. While direct data file storage techniques may be combined with techniques of the present application, embodiments of the present invention generally use logical addresses to manage data within the memory array, not file identifiers as used in direct data file storage.
In another example, a memory system according to an embodiment of the present invention stores files in one or more dedicated metablocks and one common block in the memory array so that when the file is no longer needed by the host, the dedicated metablocks may be erased immediately for reuse and the common block may be scheduled for garbage collection. Directory and FAT information sent by the host generally indicates when the host has deleted a file by removing the Directory entry for that file. In some cases, FAT entries may reflect this deletion. A memory system may determine from the directory that a file has been deleted by the host and therefore, any metablock containing only data from that file may be erased. Such a metablock may be added to a queue of metablocks to be erased at this point as part of ongoing reclaim operations. Similarly, a common block containing data from the file may be added to a queue of metablocks to be garbage collected so that the space occupied by obsolete data can be reclaimed. When the memory system has information regarding the host's deletion of files and those files are stored in metablocks in a contiguous manner with many metablocks containing data from only one file, reclaim operations may be scheduled in an efficient manner. Examples of such scheduling are given in U.S. patent application Ser. No. 11/259,423, entitled �Scheduling of reclaim operations in non-volatile memory,� filed on Oct. 25, 2005.
One advantage of a notification scheme based on FAT and directory sectors is that it uses signals that are already in general use in an LBA interface. The FAT and directory sectors are sent at different times compared with many prior systems, but they contain valid information and are generally compatible with prior LBA interfaces. Thus, a host using a notification scheme according to an embodiment of the present invention would be compatible with a memory system that did not use such a notification scheme. Such a memory system would store the FAT and directory sectors without using them to determine where sectors of host data were stored. FAT sectors stored in this way are valid because they contain entries for clusters of data that have already been stored. Thus, in the case of an unexpected loss of power, the FAT data stored in the nonvolatile memory will not be in error. The incomplete nature of the FAT information for a file may indicate that the memory system had not completed storing data for that file when power was lost.
While the examples given above use sectors of control data (FAT and directory) to send allocation information, other information may also be sent by a host using signals that are compatible with existing logical interfaces. Sending two or more identical FAT sectors may indicate subsequent host behavior to a memory system. In one example, a host may indicate to a memory system that the host does not require immediate access to the memory system and that power will be maintained. This may be indicated by sending duplicate FAT sectors in succession. Only one of these sectors may be written by the memory system, or both may be written. In response to receiving duplicate FAT sectors, the memory system determines that power will be maintained and the host does not require any immediate access, so the memory system may enter an idle state. In an idle state, the memory system may perform housekeeping operations such as reclaim operations to garbage collect metablocks containing obsolete data and consolidate metablocks containing unwritten portions. An idle state is terminated by receipt of another host command. The memory system may indicate a busy status to the host while carrying out housekeeping operations in idle mode. A busy status indicator informs the host that the memory system is carrying out housekeeping operations, but does not prevent the host from sending a command to terminate housekeeping operations and start executing the new command. In another example, a host may indicate an imminent power-down by sending an identical FAT sector three times. The memory system may react to such a signal by entering a shut-down state. In this state, the memory system indicates a busy status to the host until it has stored any data in nonvolatile memory that was not yet stored and performed any other operations to make it safe to power down. The host waits until the memory system is no longer busy before removing power. Other host behavior may also be indicated by a host by sending multiple identical FAT or directory sectors. A host may also identify a particular file for deletion using repeated sectors of control information. When a memory system receives an indication from a host that a particular file should be deleted, the file is put in a queue for garbage collection. Similarly, a host may identify a particular file for erase using repeated sectors of control information. When a memory system receives an indication from a host that a particular file should be erased, the memory system puts the file in a queue for garbage collection and immediately proceeds to perform garbage collection to remove all the data of the file from the nonvolatile memory array.
Where a memory system has the capability to use notification signals but is connected to a host that does not provide such notification signals, the memory system determines that the host does not provide notification signals and then stores data in a manner that does not require such signals. The memory system may make this determination when it first receives communication from a host. For example if the memory system receives sectors of data to be written without any prior FAT or directory sectors, then the memory may determine that the host is not enabled for such signals and may select a data storage scheme that ignores the file allocation of sectors in choosing where to store them. In one example an �identify drive� command from a host allows a host to determine whether a memory system is capable of using notification signals. The memory system returns information in response to an �identify drive� command that includes whether it has this capability. A default data storage scheme for use by a memory system connected to a host that does not support notification signals may store data as shown in FIG. 7 without regard to the file allocation of a particular sector. Examples of such storage schemes are provided in U.S. patent application Ser. No. 10/750,155, filed on Dec. 30, 2003; Nos. 10/917,888; 10/917,867; 10/917,889 and 10/917,725, filed on Aug. 13, 2004.
In another embodiment, a notification scheme may not be limited to communication according to an existing interface. Additional commands, not complying with an existing interface, may be defined for providing allocation information from a host to a memory system. Hosts and cards using such additional commands generally require a hand-shaking routing when first connected so that they can identify that the use of such additional commands is possible. In general, hosts and cards capable of using such additional commands will also be capable of operating without additional commands when connected to a host or card that does not have the capability to use the additional commands. Thus, backward compatibility is maintained for memory systems and hosts using any such new commands. Additional commands may also be provided that are not related to conveying file allocation information. For example, an explicit command may be defined for a host to erase or delete a particular file.
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No. 11/300,568 on Sep. 21, 2007, 17 pages.* Cited by examinerClassifications U.S. Classification711/103, 711/203, 711/E12.001International ClassificationG06F12/00, G06F9/34, G06F13/00, G06F9/26, G06F13/28Cooperative ClassificationG06F3/0643, G06F3/0679, G06F2212/7202, G06F3/0605, G06F12/0246European ClassificationG06F12/02D2E2, G06F3/06A2A2, G06F3/06A4F4, G06F3/06A6L2FLegal EventsDateCodeEventDescriptionJun 25, 2014FPAYFee paymentYear of fee payment: 4May 26, 2011ASAssignmentOwner name: SANDISK TECHNOLOGIES INC., TEXASFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:SANDISK CORPORATION;REEL/FRAME:026350/0829Effective date: 20110404Feb 24, 2006ASAssignmentOwner name: SANDISK CORPORATION, CALIFORNIAFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:SINCLAIR, ALAN WELSH;REEL/FRAME:017287/0200Effective date: 20051208RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services