Abstract:
A device for integrating file systems includes a plurality of storage device interfaces. Each storage device interface is operatively coupleable to a corresponding storage device, and each storage device has a corresponding storage device file system. The device also includes a host interface and a hub configured for operatively connecting between the storage device interfaces and the host interface. The hub is operative to create a virtual file system that aggregates the storage device file systems. The virtual file system is configured to represent to a host, via the host interface, each file of a first group and to refrain from representing to the host each file of a second group, where the files are stored in one or more of the plurality of storage devices. Each file of the first group satisfies a first condition and each file of the second group fails to satisfy the first condition.

Description:
REFERENCE TO EARLIER-FILED APPLICATIONS 
     This application claims priority from U.S. patent application Ser. No. 11/968,202, filed Jan. 2, 2008, the contents of which is incorporated by reference herein in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure is generally related to integrating file systems. 
     BACKGROUND 
     Despite the increased storage capacities of newly developing storage devices, such as the most recent versions of a USB flash drive, a user&#39;s storage needs will often exceed that which was once adequate. At that point, the user wanting to increase storage capacity has various options. One option is to obtain a new storage device with a greater capacity, when such a storage device becomes available, and the user will then have the task of transferring all existing stored data from the old storage device to the new storage device. The old storage device then becomes an unused resource. 
     Another option for a user wanting to increase storage capacity is to obtain additional storage devices and store data on the old and new devices. The user then has to manage data that is stored on multiple storage devices. The task can become burdensome as the user needs to access more and more file systems instead of one, which is the case when a single storage device has enough capacity for all the user&#39;s needs. 
     It would be desirable to be able to increase a host&#39;s storage capacity by using multiple storage devices and to be able to combine the device contents into a unified file system regardless of any difference in the file system formats of the underlying storage devices. 
     SUMMARY 
     The present inventors have developed devices and methods for integrating file systems, which enable a user to increase storage capacity for a host by using multiple storage devices and virtualizing the device contents into a single file system regardless of any difference in the device file systems. 
     According to an example embodiment, a device for integrating file systems includes one or more storage device interfaces, a host interface, and a hub. The storage device interfaces are for storage devices, each of which has a storage device file system. The hub is operationally connected to the storage device interfaces and to the host interface, and the hub is operative to create a virtual file system that aggregates the storage device file systems. The virtual file system may aggregate the storage device file systems according to one or more first conditions, at least one of which may be a host-level condition or a file-level condition. The hub may be further operative to distribute the contents of a file received from the host interface to at least two of the storage devices and to represent the file in the virtual file system as an undivided entity. Alternatively, the hub may be further operative to route the contents of a file received from the host interface to only one of the storage devices according to one or more second conditions. 
     The device may have additional features. For example, at least one of the storage device interfaces may comply with the USB standard. Also, the host interface may be a wired interface, and the wired interface may comply with the USB standard. The host interface may be a wireless interface. The hub may be further operative to create and maintain redundant file systems. 
     According to an example embodiment, a method of integrating file systems includes reading file systems of two or more storage devices, interpreting the file systems, creating a logical structure containing the data in the interpreted file systems, and generating in a memory sectors that map the logical structure into a virtual file system. The reading of the file systems may include communicating in compliance with the USB standard. The logical structure may be created according to one or more first conditions, at least one of which can be a host-level condition or a file-level condition. The method may include creating and maintaining a redundant file system. 
     The method may further include representing a file in the virtual file system as an undivided entity, wherein the contents of the file are distributed across two or more of the storage devices. Alternatively, the method may further include routing the contents of a file received from a host to only one of the storage devices according to one or more second conditions. 
     The method may further include representing the virtual file system to a host through a wired interface, and the wired interface may comply with the USB standard. Alternatively, the method may include representing the virtual file system to a host through a wireless interface. 
     Example embodiments are described in detail below with reference to the accompanying drawings, which are briefly described as follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a system including a file system integrator in accordance with a first example embodiment; 
         FIG. 2  illustrates a system including a file system integrator in accordance with an alternate example embodiment; and 
         FIG. 3  illustrates a flow chart representing a method of integrating file systems in accordance with an example embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The claims below will be better understood by referring to the present detailed description of example embodiments. This description is not intended to limit the scope of claims but instead to provide examples. Described first is an exemplary embodiment of a file system integrator. Described next is an alternate exemplary embodiment of a file system integrator. Also presented is a method of integrating file systems. 
       FIG. 1  illustrates, in accordance with an exemplary embodiment, a file system integrator  10  in combination with storage devices  12   a ,  12   b , and  12   c  and a host  14 . Non-limiting examples of storage devices in this system include USB flash drives, compact disks (CDs), and DVDs. The host  14  shown in  FIG. 1  is a personal computer, but other hosts that can be fashioned to operate with the file system integrator include, e.g., vehicle entertainment systems and DVD players. The file system integrator  10  enables a user to integrate file systems regardless of any differences in the individual file systems (e.g., in the file system formats) of the attached storage devices. 
     The file system integrator  10  includes storage device interfaces  16   a ,  16   b , and  6   c , a host interface  18 , and a hub  20 . The storage device interfaces  16   a ,  16   b , and  16   c  connect the storage devices  12   a ,  12   b , and  12   c , respectively, to the hub  20 . Each of the storage devices  12   a ,  12   b , and  12   c  has a storage device file system. The hub  20  is also connected to the host interface  18 . The hub  20  can be implemented as hardware, software, firmware, or any combination thereof. In this example embodiment, the hub  20  includes a controller  24 , which has a RAM  25 . Although this example embodiment involves three storage devices and three corresponding storage device interfaces, it will be understood that the number of storage devices and corresponding storage device interfaces is not limited to this. 
     Upon connection of the storage devices  12   a ,  12   b , and  12   c , a controller  24  of the hub  20  creates a virtual file system that aggregates the individual storage device file systems. The virtual file system may operate to aggregate the storage device file systems according to special conditions. Such operation can be useful in situations where system resources did not need to be used to aggregate the information of files that would not be used by a particular host. For example, if the file system integrator  10  were intended for a host that is a DVD player, the file system could operate according to a special condition whereby the file system disregards during aggregation any information relating only to files that the DVD player could not read. The resulting virtual file system would represent to the DVD player only the files that it could read. 
     The hub  20  may store a file from the host  14  by distributing the contents of the file to at least two of the storage devices  12   a ,  12   b , and  12   c . The stored file would nonetheless be represented in the virtual file system as an undivided entity. Distributing file contents among multiple storage devices is useful, for example, when none of the storage devices  12   a ,  12   b , and  12   c  individually has enough free space for the file, but the total amount of unused space in the storage devices collectively is enough. 
     The above example of aggregating only files in DVD format is an example of a host-level condition. The host may additionally or alternatively aggregate files according to a file-level condition. For example, if files contents from a file sent by the host  14  were previously distributed across multiple storage devices, and one of those storage devices were not presently connected to the host  14 , the complete contents of the file would not be available to the host  14 . The hub  20  may then aggregate according to the file-level condition that information relating to files in which the complete contents are not available is disregarded. 
     Alternatively, the hub  20  may be designed to route the contents of a file received from the host  14  to only one of the storage devices  12   a ,  12   b , and  12   c  according to one or more special conditions. For example, a condition could be to route the contents of a file to only one of storage devices  12   a ,  12   b  and  12   c , if a particular one of the storage devices has enough room for the file; such routing would save system resources by eliminating spanning as unnecessary. Another example condition would be to route the contents of a file to a particular storage device based on the file type; for instance, all DVD files would be stored on the storage device  12   a , all audio files would be stored on the storage device  12   b , and remaining files would be stored on the storage device  12   c.    
     According to this example embodiment, the storage device interfaces  16   a ,  16   b , and  16   c  comply with the USB standard. However, storage device interfaces complying with other standards may be implemented instead or in addition. 
     Again, according to this example embodiment, the host interface  18  complies with the USB standard, but alternate embodiments may use different wired interfaces as the host interface. As a further alternative, the host interface could be a wireless interface. 
     The hub  20  may be designed to create and maintain redundant file systems. An example of such a file system would be that of RAID (Redundant Arrays of Independent Disks) 1. RAID is an industry standard that encompasses data storage schemes that divide and/or replicate data among multiple hard drives. A number of standard schemes have evolved which are referred to as levels. The first level (designated as “RAID-1”) creates an exact copy (or mirror, or replica) of a set of data on two or more disks in a way that is transparent to the host. Hub  20  may also create and maintain redundant file systems using other ways known to those of skill in the art. 
     Although the above example embodiment includes multiple storage device interfaces  16   a ,  16   b , and  16   c , the device may be implemented as a file system integrator  26  having only one interface  16 , as shown in  FIG. 2 . The other elements of the file system integrator  26  are the same as in the first example embodiment, as represented using the same reference numbers. (Hub  20  of the file system integrator  26  also includes a controller  24  and RAM  25 , as shown in  FIG. 1 , even though for convenience these elements have been omitted from  FIG. 2 .) Note also that as with the example embodiment represented in  FIG. 1 , although the example embodiment of  FIG. 2  involves only one storage device and one storage device interface, the number of storage devices and storage device interfaces is not limited to such. 
     According to the embodiment shown in  FIG. 2 , the hub  20  still creates a virtual file system that aggregates individual storage device file systems, even though the file system integrator  26  has only one storage device interface  16 . The file system integrator  26  is able to access multiple storage devices  12   a ,  12   b , and  12   c , and hence multiple file systems, by a connection to the storage devices  12   a ,  12   b , and  12   c  through a multi-port hub  28 , such as a USB hub, which connects the storage device interface  16  using, e.g., a cable  30 . 
     In other embodiments, the file system integrator  10  or  26  can be built into the outer casing of the host  14 , with only the storage device interface  16  or interfaces  16   a ,  16   b  and  16   c  exposed. Alternatively, the file system integrator  10  or  26  can be joined to a general purpose interface, such as a USB port, of the host  14  and the ports of the multi-port hub  28  or of interfaces  16   a ,  16   b  and  16   c  can be placed in a convenient location for the user of the host  14 . 
     Another example embodiment is a method of integrating file systems, as represented by flow chart  32  in  FIG. 3 . This method may be practiced using the file system integrator  10  of  FIG. 1 , the file system integrator  26  of  FIG. 2 , or alternate apparatus. The method enables a user to integrate file systems regardless of any differences in the individual file systems. 
     As shown in  FIG. 3 , the first step in the method is to read the file systems of two or more storage devices. (Step S 1 .) 
     The next step is to interpret the file systems. (Step S 2 .) File systems are interpreted by performing logical transformations of data based on information in the file systems and on other factors, such as the type of host (for example, a DVD player or a personal computer), the identity of the user, or the presence of all parts of a spanned file. The data to be transformed does not need to be limited to those of homogenous file systems. Accordingly, file systems may be aggregated from storage devices having differing file system formats. 
     After the file systems are interpreted, a logical structure is created. (Step S 3 .) Such a logical structure may be created, e.g., analogously to how logical structures are created by using the “FORMAT” command in Windows®, or by using the “mkfs” command in Linux, or in other ways known to those of skill in the art. The logical structure created in step S 3  is then populated with the data in the interpreted file systems of step S 2 . 
     Then, sectors are generated in a memory, such as in the RAM  25  in the controller  24  of hub  20  ( FIG. 1 ). (Step S 4 ). The sectors map the logical structure into a virtual file system as seen from a host. That is, the generated sectors contain the logical structure of the virtual file system as seen from the host. 
     Variations of this method are included herein. For example, the reading of the file systems may be adapted to include communicating in compliance with the USB standard. The logical structure may be created according to conditions, such as a host-level condition or a file-level condition. The method may include creating and maintaining a redundant file system. 
     The method may include the step of representing a file in the virtual file system as an undivided entity such that the contents of the file are distributed across two or more of the storage devices. Alternatively, the method may include the step of routing the contents of a file received from a host to only one of the storage devices according to specified conditions. 
     The method may include the step of representing the virtual file system to a host through a wired interface, which may comply with the USB standard. Alternatively, the method may include representing the virtual file system to a host through a wireless interface, such as one complying with the Bluetooth or Wi-Fi standards. 
     Having thus described exemplary embodiments, it will be apparent that various alterations, modifications, and improvements will readily occur to those skilled in the art. Alternations, modifications, and improvements of the disclosed embodiments, though not expressly described above, are nonetheless intended and implied to be within the scope of the claims. Accordingly, the foregoing discussion is intended to be illustrative only; the invention is limited and defined only by the following claims and equivalents thereto.