Patent Publication Number: US-9842024-B1

Title: Flash electronic disk with RAID controller

Description:
CROSS-REFERENCE(S) TO RELATED APPLICATIONS 
     This application claims the benefit of and priority to U.S. Provisional Application 61/801,111, filed 15 Mar. 2013. This U.S. Provisional Application 61/801,111 is hereby fully incorporated herein by reference. 
     This application relates to U.S. Utility application Ser. No. 14/217,316, “Flash Array RAID in Flash Electronic Disks” which is hereby fully incorporated herein by reference and U.S. Utility application Ser. No. 14/217,291, “Direct Memory Access Controller with RAID Hardware Assist” which is hereby fully incorporated herein by reference. 
    
    
     FIELD 
     Embodiments of the invention relate generally to computer systems and more particularly to Flash Electronic Disk with RAID Controller. 
     DESCRIPTION OF RELATED ART 
     Over the last few years, the storage systems industry has witnessed an increasing trend in shifting data storage from mechanical hard disk drives (HDD) to solid state devices (SSD), the Flash Electronic Disk being one of them. This is brought about by a number of advantages in using SSD&#39;s over HDD&#39;s, the most notable ones are increased data accessing speed, increased reliability in terms of data integrity and physical stress, and prolonged wear and tear. 
     The increase in data accessing speed opened up a wide range of applications that were used to be shelved because of the memory-access bottleneck. With the coming of Flash Electronic Disks, data-intensive applications now have a chance to come into reality. The absence of rotating mechanical disks in Flash Electronic Disks allowed more memory intensive applications that are physically demanding, such as military applications, shock prone environments and the like, to come into shape. 
     Trends in the market today point to an increasing demand for SSDs because of its fast memory access speeds. Memory intensive applications, such as database interfaces, are slowly coming into shape as the memory access bottleneck is loosened up. In the advent of memory intensive applications, it is imperative that systems should have reliable and stable data integrity measures. The most reliable data integrity system to date is the RAID system, which has been applied extensively to many computer systems using HDDs. The RAID system uses a simple architecture where data is striped or mirrored to a number of disks. All possible implementations of redundancy are already considered in its many configurations. These principles can also be applied to flash electronic disks to boost data integrity. 
     Conventional RAID systems prefer implementing RAID Controllers as a separate hardware entity. This is because RAID controls are computations-extensive, that when implemented in firmware, a big chunk of the CPU resource is eaten up. This invention helps to unload the firmware of a computational burden, as this invention implements RAID in hardware, but it takes it a step further. There will be no separate hardware entity for the RAID controls as it will all be integrated into the disk itself, producing a Flash Electronic Disk that is also a RAID Controller at the same time. 
     SUMMARY 
     The Flash Electronic Disks are known for its stable and reliable performance over traditional HDDs due to the absence of mechanical components. An embodiment of this invention aims to fortify the existing data integrity badge of Flash Electronic Disks by integrating RAID measures into the disk. Flash Electronic Disks in a RAID configuration would be by far, the most reliable storage system to date. 
     An embodiment of this invention presents a method and system for implementing RAID for Flash Electronic Disks. The invention integrates RAID control mechanisms into the Flash Electronic Disk controllers, eliminating the need for a separate RAID controller hardware, with minimal firmware intervention. The system and method uses the principles of RAID in addressing the issues brought about by physical disk crashes. The invention merges the benefits of using Flash Electronic Disks and the capabilities of RAID in data integrity, such as hot pluggable disks, into a Flash Electronic Disk. The system and method supports all RAID levels via configurable RAID controller. The system and method also provides possible RAID configurations for the disks over generic IO Interfaces. 
     In another embodiment of the invention, a method and system for implementing a Flash Electronic Disk with support for Redundant Array of Inexpensive Disks (RAID) system is presented. The method and system include a RAID Control Module that interprets RAID commands from any Host, an Exclusive-Or (XOR) Engine for RAID commands with parity computations, a RAID Cache for temporary storage during calculations, and possible RAID configurations for the Flash Electronic Disks via generic IO interfaces such as SATA, SCSI or PCI Express (PCIe). The invention presents a Flash Electronic Disk that is capable of executing RAID Master and Slave functions over conventional links without the need for a separate RAID Controller hardware and without extensive use of firmware processing. 
     A key idea of embodiments of this invention lies on having Flash Electronic Disks that offer data integrity capabilities of RAID in highly flexible configurations, without sacrificing the high memory accessing speed of Flash Electronic Disks. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       So that the manner in which the above recited features, advantages and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. 
       It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the present invention may admit to other equally effective embodiments. 
         FIG. 1  shows a typical prior art Flash Electronic Disk System. 
         FIG. 2  shows a typical prior art RAID system and its components. 
         FIG. 3  illustrates a write operation implementation for a typical prior art RAID-5 system. 
         FIG. 4  illustrates a read operation implementation for a typical prior art RAID-5 system. 
         FIG. 5  illustrates a read-modify-write operation implementation for a typical prior art RAID-5 system. 
         FIG. 6  illustrates the modified Flash Electronic Disk Architecture according to an embodiment of the present invention. 
         FIG. 7  shows a RAID system consisting of ordinary disks and the Flash Electronic Disk according to an embodiment of the present invention. 
         FIG. 8  is the write operation implementation in a Flash Electronic Disk taking a master role in a RAID-5 system according to an embodiment of the present invention. 
         FIG. 9  illustrates how the Flash Electronic Disk performs the flushing process according to an embodiment of the present invention. 
         FIG. 10  is the read operation implementation in a Flash Electronic Disk taking a master role in a RAID-5 system according to an embodiment of the present invention. 
         FIG. 11  is the read-modify-write operation implementation in a Flash Electronic Disk taking a master role in a RAID-5 system according to an embodiment of the present invention. 
         FIG. 12  is the write operation implementation in a Flash Electronic Disk taking dual roles in a RAID-5 system according to an embodiment of the present invention. 
         FIG. 13  is the read operation implementation in a Flash Electronic Disk taking dual roles in a RAID-5 system according to an embodiment of the present invention. 
         FIG. 14  is the read-modify-write operation implementation in a Flash Electronic Disk taking dual roles in a RAID-5 system according to an embodiment of the present invention. 
         FIG. 15  is a possible configuration of four Flash Electronic Disks in a RAID System according to an embodiment of the present invention. 
         FIG. 16  summarizes the multi-RAID configuration of multiple Flash Electronic Disks according to an embodiment of the present invention. 
         FIG. 17  illustrates a method to operationally integrate one or more RAID control mechanisms into a flash electronic disk controller, in accordance with one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the various embodiments of the present invention. Those of ordinary skill in the art will realize that these various embodiments of the present invention are illustrative only and are not intended to be limiting in any way. Other embodiments of the present invention will readily suggest themselves to such skilled persons having the benefit of this disclosure. 
     In addition, for clarity purposes, not all of the routine features of the embodiments described herein are shown or described. One of ordinary skill in the art would readily appreciate that in the development of any such actual implementation, numerous implementation-specific decisions may be required to achieve specific design objectives. These design objectives will vary from one implementation to another and from one developer to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would nevertheless be a routine engineering undertaking for those of ordinary skill in the art having the benefit of this disclosure. The various embodiments disclosed herein are not intended to limit the scope and spirit of the herein disclosure. 
     Preferred embodiments for carrying out the principles of the present invention are described herein with reference to the drawings. However, the present invention is not limited to the specifically described and illustrated embodiments. A person skilled in the art will appreciate that many other embodiments are possible without deviating from the basic concept of the invention. Therefore, the principles of the present invention extend to any work that falls within the scope of the appended claims. 
     As used herein, the terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items. 
       FIG. 1  shows a typical prior art Flash Electronic Disk architecture. A Flash Electronic Disk  103  is composed mainly of Flash Memory Devices  104 , linked to the Flash Controller  102  by a Flash Interconnect  101 . The Flash Interconnect  101  handles the necessary data passing sequences between the Host  100  and the Flash Memory Devices. The Host  100  is typically a CPU of a computer system which sends out instructions to the disk via the IO Bus  105 . The Flash Electronic Disk  103  mimics an ordinary HDD so that the Host  100  sees it as an ordinary storage device. The Host issues read and write commands to the Flash Electronic Disk as if it is just accessing an ordinary HDD. The Flash Controller  102  of the Flash Electronic Disk translates the instructions from the Host  100  into flash native commands which are understood by the plurality of Flash Memory Devices  104 .  FIG. 1  describes a typical storage device system, though in this case, the storage device uses flash memory devices instead of the conventional rotating mechanical disks. 
       FIG. 2  illustrates a typical prior art RAID system and its components. A RAID system has a RAID Controller  207  that manages a plurality of Slave Disks  205  and makes them appear as just one storage device to the Host  200 . Host  200  is usually a computer CPU that sends out memory transfer instructions to the RAID system  201 . In general, the RAID Controller handles all system-related activities such as communicating to the host, accessing the slave disks, maintaining system information, executing requested transfers and recovering from disk failures. A typical RAID system distributes its data across all the slave disks in a manner commonly referred to as data striping. By allowing more than one slave disk in the system, RAID allows for concurrent access by independent processes. RAID has 5 distinct levels/configurations for redundancy; some users though combine these configurations to produce hybrids that suit their purpose. Most RAID levels employ parity for redundancy, thus requiring the use of combinational logic to implement the equivalent of an Exclusive-OR (XOR) Engine  203 , which is a processing element that performs parity calculations. The RAID Cache  206  is the temporary storage of data commonly used for RAID parity operations. The Mapping Table  202  is used by the RAID Controller  207  to determine which slave disk(s) are being referred to by the request. The Mapping Table  202  is used to translate the logical block addresses specified in the commands received from the Host  200  into addresses that point to the actual physical disk locations. The Mapping Table  202  is created based on the RAID system configuration. The plurality of Slave Disks  205  and the RAID Controller  207  are linked together via IO Bus  204 , which could include any of the existing IO interfaces available today, such as SCSI, SATA, PCIe, or an equivalent interface. 
       FIG. 3  illustrates a write operation implementation for a typical prior art RAID-5 system. RAID-5 is one of the most common protection techniques against failed disks. This RAID configuration works by striping data and parity information across all the slave disks. In  FIG. 3 , Host  300  issues a write command  308  to the RAID Controller  307 . The write data  309  is stored in the RAID Cache  306 . The RAID Controller after referring to its Mapping Table  302  determines that the write data in the RAID Cache  306  should be striped across the plurality of slave disks  305 . The RAID Controller issues an IO write command  310  to write data stripe  0   314  to Slave Disk  1   318 , an IO write command  311  to write data stripe  1   315  to Slave Disk  2   319  and an IO write command  312  to write data stripe  2   316  to Slave Disk  3   320 . The RAID Controller also generates the corresponding parity stripe  317  by XORing the data stripes. This parity stripe is written by the RAID Controller to Slave Disk N  321  by issuing another IO write command  313 . 
       FIG. 4  illustrates a read operation implementation for a typical prior art RAID-5 system. Host  400  issues a read command  408  to the RAID Controller  407 . The RAID Controller checks its Mapping Table  402  to determine from which slave disks  405  the data will come from. The RAID controller then issues an IO read command  414  to Slave Disk  1   410  to get data stripe  417 , an IO read command  415  to Slave Disk  2   411  to get data stripe  418  and an IO read command  416  to Slave Disk  3   412  to get data stripe  419 . These data stripes are stored and reconstructed in RAID Cache  406  before being sent to the Host  400  as the read data  409 . In some cases, parity checking is performed during read operation in which case the parity stripe is read from the other disk and then XORed to all the data stripes read from the rest of the slave disks. 
       FIG. 5  illustrates a read-modify-write operation implementation for a typical prior art RAID-5 system. Read-modify-write occurs whenever the Host requests to write only a data stripe instead of the whole data block. Host  500  sends a write command  512  to the RAID Controller  507 . The RAID Controller receives the write data  513  and stores it in the RAID Cache  506 . After referring to the Mapping Table  502 , the RAID Controller discovers that the write request involves a write of only a data stripe. The RAID Controller then issues an IO read command  514  to the Slave Disk  1   508  to read the old data stripe  515 . The old data stripe  515  is XORed with the new data stripe stored in the RAID Cache  506  using the XOR Engine  503 . The result of the XOR operation is temporarily stored in the RAID Cache  506 . The new data stripe is still kept in the RAID Cache. The RAID Controller then issues an IO read command  518  to the Slave Disk N  511  to read the old parity  519 . The old parity  519  is then XORed with the result of the previous XOR operation using the XOR Engine  503 . The result of this XOR operation, the new parity, is again stored in the RAID Cache  506 . After generating the new parity, the RAID Controller  507  issues an IO write command  516  to the Slave Disk  1   508  to write the new data stripe  517  from the RAID Cache  506 . The RAID Controller also issues an IO write command  520  to the Slave Disk N  511  to write the new parity  521  from the RAID Cache  506 . This completes the read-modify-write operation. 
       FIG. 6  illustrates the modified Flash Electronic Disk Architecture. In this invention, the RAID features are incorporated into the Flash Electronic Disk by adding the RAID components in the Flash Controller. The Flash Electronic Disk  608  is upgraded with the addition of the RAID Control Module  607 , which handles the RAID capabilities of the invention. The RAID Control Module contains an XOR Engine  603  that is used during parity calculations, a RAID Cache  606  that serves as the temporary data storage during parity calculations and a Mapping Table  602  for address translation of the commands received from the Host  600 . 
     In a computer system where RAID is needed, the Flash Electronic Disk in  FIG. 6  becomes a ready RAID Controller eliminating the need for a separate hardware entity. The plurality of Flash Memory Devices  605  serves as the non-volatile cache of the RAID system. The Flash Memory Devices are used to store recently used information for the RAID system. The Flash Controller  601  partitions the Flash Memory Devices  605  into stripes and records the boundaries. The Flash Controller passes these boundaries to the RAID Control Module  607  for inter-disk striping of RAID. The use of these flash memory devices as cache significantly enhances the performance of the RAID system because they reduce frequent access to slower storage devices such as HDD. 
     The Flash Electronic Disk of  FIG. 6  is also capable of handling master and slave roles in a RAID system. The plurality of Flash Memory Devices  605  may be used as a slave disk instead of a cache. The memory locations of the Flash Memory Devices are remapped on a new addressing scheme kept by the RAID Control Module  607  in its Mapping Table  602 . In addition, it is possible to distribute the flash memory devices to a number of RAID systems. The Flash Electronic Disk can have one flash memory device assigned to its RAID Control Module  607 , and the rest of its Flash Memory Devices  605  assigned to different RAID controllers in other RAID systems. This way, the Flash Electronic Disk  608  can participate in multiple RAID systems rather just one, and can also take dual roles depending on which RAID system it is in. 
     Furthermore, the plurality of Flash Memory Devices  605  can be configured as replacement disks or “hot spares”. The availability of replacement disks allows the RAID Control Module  607  to perform reconstruction. Reconstruction is a background process executed in the RAID system to regenerate the data from the failed disk. This process involves reading the data from the surviving slave disks for each stripe, calculating the parity of that data and then writing this value to the replacement disk. Reconstruction works both for data and parity disks since the XOR operation is commutative. The performance of the RAID system is degraded while a failed disk is being rebuilt. However, the RAID system continues to function in such a way that all data are still accessible by the Host including that from the failed disk. 
       FIG. 7  shows a RAID system consisting of ordinary disks and the Flash Electronic Disk according to an embodiment of the present invention. The Flash Electronic Disk is labeled as the “Master Disk”  704  to differentiate it from the Slave Disks  710  in the RAID system  711 . The RAID Control Module  709  of the Master Disk  704  is configured to be the RAID Controller of the RAID system  711 . The Master Disk  704  comprising of a Flash Controller  703  along with the Flash Interconnect  706  and the plurality of Flash Memory Devices  707 , used as the system cache, communicates with the Slave Disks  710  through the one or more generic IO Bus  701 , such as SCSI, SATA, PCIe, or an equivalent IO Bus. The slave disks of the RAID system  711  may be any other disk, HDD or SSD, as long as it can interface with the one or more IO Bus  701 . The RAID Control Module  709  has its own XOR Engine  705  for parity calculations, a RAID Cache  708  for temporary storage of data and a Mapping Table  702  for translating the commands received for the RAID system. 
       FIG. 8  is the write operation implementation in a Flash Electronic Disk taking a master role in a RAID-5 system according to an embodiment of the present invention. The Master Disk  804  receives a write command  812  from the Host  800 . The write data  813  is stored in the RAID Cache  808  of the RAID Control Module  809 . The RAID Control Module after referring to its Mapping Table  802  determines that the write data in the RAID Cache  808  should be striped across the plurality of slave disks  810 . The RAID Control Module translates the write request received from the Host  800  into multiple write accesses to the plurality of slave disks by converting the write data  813  into data stripes. The RAID Control Module also generates the corresponding parity stripe by XORing all the data stripes using its XOR Engine  805 . This parity stripe is temporarily stored in the RAID Cache  808  along with the data stripes. 
     However, instead of accessing the slave disks frequently, the Master Disk  804  decides to first write the data stripes to its Flash Memory Devices  807 . The Flash Memory Devices  807 , being the system cache, contains the recently used information for the RAID system  811 . The Flash Controller  803  therefore issues a flash write command  814  to write data stripe  0   818  to Flash Memory Device  1   822 , a flash write command  815  to write data stripe  1   819  to Flash Memory Device  1   823  and a flash write command  816  to write data stripe  2   820  to Flash Memory Device  1   824 . The Flash Controller also issues a flash write command  817  to write the parity stripe  821  to Flash Memory Device N  825 . The data and parity stripes stored in the plurality of Flash Memory Devices  807  are periodically flushed to the plurality of Slave Disks  810 . 
       FIG. 9  illustrates how the Flash Electronic Disk performs the flushing process according to an embodiment of the present invention. The plurality of the Flash Memory Devices  907  acts as the system cache of the RAID system  911 . The contents of the Flash Memory Devices are regularly transferred to the Slave Disks. Flash Memory Device  1   920  is the cache of the Slave Disk  1   932 . Flash Memory Device  2   921  is the cache of the Slave Disk  2   933 . Flash Memory Device  3   922  is the cache of the Slave Disk  3   934 . Flash Memory Device N  923  is the cache of the Slave Disk N  935 . During flushing, the Flash Controller  903  issues a flash read command  912  to Flash Memory Device  1   920  to transfer the data block  0   916  to the RAID Cache  908 . The Flash Controller then issues an IO write command  928  to Slave Disk  1   932  to transfer the same data block  0   924  from RAID Cache  908  to Slave Disk  1   932 . In the same way, the Flash Controller  903  issues a flash read command  913  to Flash Memory Device  2   921  to transfer the data block  1   917  to the RAID Cache  908 . The Flash Controller then issues an IO write command  929  to Slave Disk  2   933  to transfer the same data block  1   925  from RAID Cache  908  to Slave Disk  2   933 . For Flash Memory Device  3   922 , the Flash Controller  903  issues a flash read command  914  to Flash Memory Device  3   922  to transfer the data block  2   918  to the RAID Cache  908 . The Flash Controller then issues an IO write command  930  to Slave Disk  3   934  to transfer the same data block  2   926  from RAID Cache  908  to Slave Disk  3   934 . And lastly for Flash Memory Device N  923 , the Flash Controller  903  issues a flash read command  915  to Flash Memory Device N  923  to transfer the data block N- 1   919  to the RAID Cache  908 . The Flash Controller then issues an IO write command  931  to Slave Disk N  935  to transfer the same data block N- 1   927  from RAID Cache  908  to Slave Disk N  935 . 
       FIG. 10  is the read operation implementation in a Flash Electronic Disk taking a master role in a RAID-5 system according to an embodiment of the present invention. Host  1000  issues a read command  1012  to the Master Disk  1004 . The RAID Control Module  1009  determines that the requested data is striped across the plurality of slave disks  1010 . The RAID Control Module translates the read request received from the Host  1000  into multiple read accesses to the plurality of slave disks by reading the corresponding data stripes. The RAID Control Module  1009  of the Master Disk checks its Mapping Table  1002  to determine from which slave disks  1010  the data stripes will come from. 
     However, instead of accessing the slave disks frequently, the Master Disk  1004  in one embodiment can decide to read the data stripes from its Flash Memory Devices  1007 . The Flash Memory Devices  1007 , being the system cache, contains the recently accessed information for the RAID system  1011 . The Flash Controller  1003  therefore issues a flash read command  1014  to Flash Memory Device  1   1020  to get data stripe  1017 , a flash read command  1015  to Flash Memory Device  2   1021  to get data stripe  1018  and a flash read command  1016  to Flash Memory Device  3   1022  to get data stripe  1019 . These data stripes are stored and reconstructed in RAID Cache  1008  before being sent to the Host  1000  as the read data  1013 . 
       FIG. 11  is the read-modify-write operation implementation in a Flash Electronic Disk taking a master role in a RAID-5 system according to an embodiment of the present invention. Host  1100  sends a write command  1112  to the Master Disk  1104 . The RAID Control Module  1109  of the Master Disk receives the write data  1113  and stores it in the RAID Cache  1108 . After referring to the Mapping Table  1102 , the RAID Control Module discovers that the write request involves a write of only a data stripe. A write of only a data stripe involves a read-modify-write operation. The RAID Control Module first checks from which slave disks will the old data stripe and old parity stripe come from. The RAID Control Module determines that the old data stripe should come from Slave Disk  1  and the old parity stripe should come from Slave Disk N. 
     However, instead of accessing the slave disks frequently, the Master Disk  1104  decides to read these stripes from its Flash Memory Devices  1107 . The Flash Memory Devices  1107 , being the system cache, contains the recently accessed information for the RAID system  1111 . The Flash Controller  1103  therefore issues a flash read command  1114  to the Flash Memory Device  1   1122  to read the old data stripe  1118 . The old data stripe  1118  is XORed with the new data stripe  1113  stored in the RAID Cache  1108  using the XOR Engine  1105 . The result of the XOR operation is temporarily stored in the RAID Cache  1108 . The new data stripe is still kept in the RAID Cache. The Flash Controller then issues a flash read command  1116  to the Flash Memory Device N  1125  to read the old parity  1120 . The old parity  1120  is then XORed with the result of the previous XOR operation using the XOR Engine  1105 . The result of this XOR operation, the new parity, is again stored in the RAID Cache  1108 . After generating the new parity, the Flash Controller  1103  issues a flash write command  1115  to the Flash Memory Device  1   1122  to write the new data stripe  1119  from the RAID Cache  1108 . The Flash Controller also issues a flash write command  1117  to the Flash Memory Device N  1125  to write the new parity  1121 . 
       FIG. 12  is the write operation implementation in a Flash Electronic Disk taking dual roles in a RAID-5 system according to an embodiment of the present invention. In this implementation, the RAID Control Module  1209  of the Master Disk  1204  is configured as the RAID Controller of the RAID system  1211 . The Flash Memory Device  1   1212  of the Master Disk, along with the Slave Disks  1220 ,  1221 ,  1222  act as the RAID Slave Disks with the data striped across all the slave disks. 
     The Flash Controller  1203  of the Master Disk  1204  receives a write command  1218  along with the write data  1219  from the Host  1200 . The Flash Controller stores the write data  1219  it received from the Host  1200  in the RAID Cache  1208 . Based from the Mapping Table  1202  of the RAID Control Module  1209 , the data sent by the Host  1200  should be striped across all the RAID Slave Disks. The RAID Control Module translates the write request received from the Host  1200  into multiple write accesses by converting the write data  1219  into data stripes. The RAID Control Module also generates the corresponding parity stripe by XORing all the data stripes using its XOR Engine  1205 . This parity stripe is temporarily stored in the RAID Cache  1208  along with the data stripes. The Flash Controller  1203  then issues a flash write command  1216  to write data stripe  0   1217  to Flash Memory Device  1   1212 , an IO write command  1224  to write data stripe  1   1223  to Slave Disk  2   1220  and an IO write command  1226  to write data stripe  2   1225  to Slave Disk  3   1221 . The Flash Controller also issues an IO write command  1228  to write the parity stripe  1227  to Slave Disk N  1222 . 
       FIG. 13  is the read operation implementation in a Flash Electronic Disk taking dual roles in a RAID-5 system according to an embodiment of the present invention. In this implementation, the RAID Control Module  1309  of the Master Disk  1304  is configured as the RAID Controller of the RAID system  1311 . The Flash Memory Device  1   1312  of the Master Disk, along with the Slave Disks  1324 ,  1325 ,  1326  act as the RAID Slave Disks with the data striped across all the slave disks. 
     The Flash Controller  1303  of the Master Disk  1304  receives a read command  1318  from the Host  1300 . The RAID Control Module  1309  being the RAID Controller of the RAID system  1311  interprets the command by referring to its Mapping Table  1302 . Based from the Mapping Table, the data being requested by the Host  1300  is found to be striped across all the RAID Slave Disks. The Flash Controller then creates the corresponding Flash Read command for the Flash Memory Device and IO Read commands for the other Slave Disks. A Flash Read command  1316  is sent to Flash Memory Device  1   1312  to get the data stripe  0   1317 . An IO Read command  1321  is sent to Slave Disk  2   1324  to get the data stripe  1   1320 . An IO Read command  1323  is sent to Slave Disk  3   1325  to get the data stripe  2   1322 . The data stripes received from the Flash Memory Device and the Slave Disks are reconstructed in the RAID Cache  1308  and then sent to the requesting Host  1300  as the read data  1319 . 
       FIG. 14  is the read-modify-write operation implementation in a Flash Electronic Disk taking dual roles in a RAID-5 system according to an embodiment of the present invention. In this implementation, the RAID Control Module  1409  of the Master Disk  1404  is configured as the RAID Controller of the RAID system  1411 . The Flash Memory Device  1   1418  of the Master Disk, along with the Slave Disks  1422 ,  1423 ,  1424  act as the RAID Slave Disks with the data striped across all the slave disks. 
     Host  1400  sends a write command  1412  to the Master Disk  1404 . The RAID Control Module  1409  of the Master Disk receives the write data  1413  and stores it in the RAID Cache  1408 . After referring to the Mapping Table  1402 , the RAID Control Module discovers that the write request involves a write of only a data stripe. A write of only a data stripe involves a read-modify-write operation. The RAID Control Module first checks from which slave disks will the old data stripe and old parity stripe come from. The RAID Control Module determines that the old data stripe should come from Flash Memory Device  1  and the old parity stripe should come from Slave Disk N. 
     The Flash Controller  1403  issues a flash read command  1417  to the Flash Memory Device  1   1418  to read the old data stripe  1416 . The old data stripe  1416  is XORed with the new data stripe  1413  stored in the RAID Cache  1408  using the XOR Engine  1405 . The result of the XOR operation is temporarily stored in the RAID Cache  1408 . The new data stripe is still kept in the RAID Cache. The Flash Controller then issues an IO read command  1425  to the Slave Disk N  1424  to read the old parity  1426 . The old parity  1426  is then XORed with the result of the previous XOR operation using the XOR Engine  1405 . The result of this XOR operation, the new parity, is again stored in the RAID Cache  1408 . After generating the new parity, the Flash Controller  1403  issues a flash write command  1414  to the Flash Memory Device  1   1418  to write the new data stripe  1415  from the RAID Cache  1408 . The Flash Controller also issues an IO write command  1428  to the Slave Disk N  1424  to write the new parity  1427 . 
       FIG. 15  is a configuration of four Flash Electronic Disks in a RAID System according to an embodiment of the present invention. Each of the four Flash Electronic Disks  1500 ,  1501 ,  1502  and  1503  has a RAID Control Module  1504 ,  1505 ,  1506  and  1507 . All other disk modules are hidden, as the focus is on the role of the RAID Control Modules. The Flash Electronic Disks are interconnected via the one or more generic IO Interface. If the Flash Memory Devices in each Flash Electronic Disk are partitioned in such a way that it allows multiple RAID systems to access it, each Flash Electronic Disk can participate in multiple RAID systems and take on dual roles—RAID Master or Slave Disk. For example, Host  0   1508  configures Flash Electronic Disk  0   1500  to become a RAID Controller with Flash Electronic Disk  1   1501 , Flash Electronic Disk  2   1502  and Flash Electronic Disk  3   1503  as its slave disks. For clarity, the RAID system defined by Host  0   1508  is labeled as RAID System  0 . Under RAID System  0 , the RAID Control Modules  1505 ,  1506 , and  1507  take on the Slave mode. In RAID System  1 , Host  1509  configures the RAID Control Module  1505  to take the Master role while RAID Control Modules  1504 ,  1506  and  1507  take slave roles. The same goes for RAID System  2  which has  1510  as the Host and RAID Control Module  1506  as its Master, and RAID System  3  which has  1511  as the Host and  1507  as the RAID Control Module.  FIG. 15  shows a possible configuration of Flash Electronic Disks in one embodiment employing the invention used to its full potential in RAID systems. It shows 4 computer systems using four Flash Electronic Disks in four distinct RAID Systems  0 ,  1 ,  2  and  3 . 
       FIG. 16 . summarizes the multi-RAID configuration of multiple Flash Electronic Disks according to an embodiment of the present invention. Column  1602  lists the Flash Electronic Disks  0 ,  1 ,  2 ,  3 , and N respectively in rows  1620 ,  1622 ,  1624 ,  1626 , and  1628 . Columns  1604 ,  1606 ,  1608 ,  1610 , and  1612  list the Raid System  0 ,  1 ,  2 ,  3 , and N, respectively. More Flash Electronic Disks can be added to the configuration of  FIG. 15  to produce multiple RAID systems on a plurality of disks. The RAID system becomes more stable and data integrity is high. The configuration also allows non flash electronic disks to be inserted into the RAID system, as long as it conforms to the IO Interface, but its role will be limited only to being a slave, and its address map is limited only to the RAID system where its RAID Controller is attached to. 
       FIG. 17  illustrates a method to operationally integrate one or more RAID control mechanisms into a flash electronic disk controller, in accordance with one embodiment of the invention. The method starts in operation  1702 . Operation  1704  is next and includes incorporating one or more RAID features into a flash electronic disk by adding one or more RAID components in a flash controller, wherein the flash electronic disk is upgraded with the addition of a RAID control module to control the one or more RAID components. Operation  1706  is next and includes receiving a read or write operation command at the flash electronic disk controller from a host. Operation  1708  is next and includes translating the read or write operation command into a command format understood by one or more flash controllers. Operation  1710  is next and includes translating the command format into an instruction format understood by one or more flash memory devices. Operation  1712  is next and includes accessing one or more memory locations in the one or more flash memory devices according to the instruction format to perform a read or write operation for the host. The method ends in operation  1714 . 
     Foregoing described embodiments of the invention are provided as illustrations and descriptions. They are not intended to limit the invention to precise form described. In particular, it is contemplated that functional implementation of invention described herein may be implemented equivalently in hardware, software, firmware, and/or other available functional components or building blocks, and that networks may be wired, wireless, or a combination of wired and wireless. 
     It is also within the scope of the present invention to implement a program or code that can be stored in a machine-readable or computer-readable medium to permit a computer to perform any of the inventive techniques described above, or a program or code that can be stored in an article of manufacture that includes a computer readable medium on which computer-readable instructions for carrying out embodiments of the inventive techniques are stored. Other variations and modifications of the above-described embodiments and methods are possible in light of the teaching discussed herein. 
     The above description of illustrated embodiments of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. 
     These modifications can be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.