JP4572205B2 - Flash memory drive device, control method thereof, and program thereof - Google Patents

Description

  The present invention relates to a flash memory drive device that stores an OS and boots the OS, a control method thereof, and a program thereof, and more particularly to leveling of the number of rewrites of a flash memory.

  Conventionally, flash memory is erased and written in units of blocks, but there are cases where defective cells exist inherently at the time of semiconductor manufacturing, and blocks that have reached the rewrite life are defective. Thus, it is known that a block that cannot be written, that is, a defective block exists or appears. The bad block and the logical block are not connected to each other, and the normal logical block is always visible from the logical block.

  With the above background, as shown in FIG. 2, the flash memory can be used in a logical / physical conversion in which the physical block of the actual flash memory is associated with the logical block notified or responding from the host computer. It is common to update a conversion table every time deletion / update / addition is performed.

  That is, when viewed from the host computer side, the physical block of the flash memory cannot be directly controlled, and all control is performed by the flash memory controller.

  Here, a general flash memory has a finite number of writable times per block. Now put it as 100,000 times. If the number of times of writing approaches or exceeds about 100,000 times, the probability of becoming the above-described defective block is remarkably increased. For this reason, the flash memory controller in the well-known technique distributes the number of rewrites per block according to the algorithms shown in FIGS.

  First, it demonstrates using FIG. When the flash memory controller receives a “data A update” command from the host computer, it reads the data of the physical block in which the data A is stored. Next, the “vacant block” for storing the data A after the update is searched. In this case, as shown in FIG. 5, assuming that the direction of searching for an empty block operates according to the rule of the descending order of the physical block, the data A is updated to the physical block 2 and the result is copied. When the writing back to the physical block 2 is completed, the original data A of the physical block 1 that is no longer needed is erased to make a free area.

  With this processing, the number of writes is distributed between the physical block 1 and the physical block 2.

  Next, a description will be added with reference to FIG. When the flash memory controller receives a “data C update” command from the host computer, it reads the data of the physical block in which the data C is stored. Next, the “vacant block” for storing the data A after the update is searched. In this case, as shown in FIG. 5, assuming that the direction of searching for an empty block operates according to the rule that the physical block descends in the same manner as described above, the data C is updated to the physical block 5 and the result is copied. When the writing back to the physical block 5 is completed, the original data A of the physical block 4 that is no longer needed is erased to make a free area.

  With this processing, the number of writes is distributed between the physical block 4 and the physical block 5.

  By repeating the above processing, writing is prevented from being concentrated on a specific physical block. That is, the number of writes is leveled for each physical block.

  However, there is a technical problem to be solved here. This will be described with reference to FIG. If there is no erase / update command from the host computer for the data B stored in the physical block 3, this block is not subject to leveling of the number of rewrites.

  Furthermore, in the prior art, a read-only file has not been a target for rewrite leveling in principle (see, for example, Patent Document 1).

FIG. 9 and FIG. 10 show transitions until the OS starts up in the flash memory device.
In FIG. 9, when the power of the host computer is turned on, the master boot record at the head of the file system group is read for the flash memory device that is the boot device. If it is recognized that the flash memory is a boot drive, the program jumps to the partition boot record as shown in FIG. 9, starts the OS loader, and starts the OS. (For example, see Patent Document 2) Even if an attempt was made to move a read-only file after the OS was started, it was difficult.
JP 2000-285001 A JP 2004-318871 A

  As described above, once the OS is started up, the OS and application software run, so that an individual file in the flash memory device is restricted by the software. For this reason, the read-only file is moved. That is, in order to read once and write back again, the OS and application program must be exclusively controlled. It is very difficult to do this.

  Therefore, as described above, in the conventional technology, the read-only file is not a target for rewrite leveling in principle, but this may be a potential problem of the existing flash memory drive device. It was.

This point will be described with reference to FIG. As shown in FIG. 6, the file structure indicated by the file structure group B type is roughly a ratio of 50% for read-only files, 25% for rewrite files, and 25% for free areas. At this time, since there are many rewrite files used for leveling the number of rewrites and free areas, the ratio of the area to be leveled for the number of rewrites is large. For this reason, the lifetime of the physical block is less than the number of erase / write cycles, and the lifetime issue is solved.
On the other hand, the configuration of the file configuration group B type shown in FIG. 7 has a ratio of approximately 70% for read-only files, 15% for rewrite files, and 15% for free areas. Compared with the file group configuration type B in FIG. 6, the ratio of the rewrite file and the free area is small, that is, the leveling target area is small. For this reason, the actual erase / write frequency exceeds the erase / write frequency life of the physical block, and the defective block is reached, resulting in a state that does not function as a device. The reason for this situation is that, in the prior art, as described above with reference to FIG. 3, the read-only file is not a target for rewrite leveling in principle.

  Therefore, the present invention aims to extend the product life of a flash memory drive device by making all storage areas including read-only files subject to rewrite leveling by making read-only files subject to rewriting.

According to a first aspect of the present invention , there is provided a flash memory drive device including a flash memory controller, which reads data from each logical block of the flash memory at the time of booting, and reads the read data into the read data. A logical block rewriting unit for writing back to the same logical block as the read logical block, and a physical block changing unit for writing back data to a physical block different from that at the time of reading when writing by the logical block writing. wherein the operated to divide the rewriting means to the multiple flash memory drive apparatus according to claim Rukoto is provided.
According to a second aspect of the present invention, there is provided a flash memory drive device including a flash memory controller, wherein data is read from each logical block of the flash memory at the time of booting, and the read data is A logical block rewriting means for writing back to the same logical block as the read logical block, a physical block changing means for writing data back to a physical block different from that at the time of reading when writing by the logical block writing, and a BIOS And a means for reading the date information from the memory, and the flash memory drive device is characterized in that the rewrite means is periodically operated based on the date information.

  In the above flash memory drive device, the logical data rewrite means is performed before the OS loader is started, so that even the read-only file or the rewrite file is the target of the write count leveling means. It may be.

  According to the present invention, some unused areas in the built-in flash memory group can be used. By programming the “rewrite process” in the unused area, this process is performed when booting, so that the number of flash memory rewrites can be leveled even for read-only files. Is possible.

Next, the best mode of the present invention will be described with reference to the drawings.
[Embodiment 1]
First, the configuration will be described with reference to FIG. 1, FIG. 9, FIG. 10, and FIG.

  The flash memory drive apparatus of the present invention is generally shown in FIG. The flash memory drive device includes a flash memory group 10 and a flash memory controller 20 for controlling the flash memory group 10. The flash memory drive device is connected to the host computer 30 via an IDE bus or the like as shown in FIG. 1, and this device is a boot device like a general HDD (hard disk drive). , OS (Operating System) is started.

  Here, as described above, FIG. 9 is a well-known technique, and shows the flow of OS startup. On the other hand, FIG. 10 shows a method for realizing the function of leveling the number of rewrites for the read-only file in the flash memory according to the present invention. FIG. 11 shows the flow of processing for realizing the present invention. By using the means of the present invention shown in FIGS. 10 and 11, it is possible to easily rewrite a read-only file into another block. The operation will be described below.

  In FIG. 10, after the boot drive recognition is completed in the master boot record, before jumping to the partition boot record, the program jumps to the place where the “block unit / rewrite” execution program is written. Since this area is assigned a portion that is originally an unallocated area, there is no problem even if the execution program is assigned.

  Next, the processing content of the “block unit / rewrite” execution program will be described with reference to FIGS. When the execution program is started, a start logical block SLB and a logical end block ELB are set (S1). The SLB and ELB are stored in the master boot record of FIG. Next, data is read in block units in order from the top of the logical block (S2), and the data is written back to the same logical block while retaining its contents (S3). Here, as shown in FIG. 2, the logical block and the physical block are converted based on the conversion table. At this time, if the conversion table is not updated, rewriting concentrates on a specific physical block, and the life of the physical block is significantly reduced. Therefore, in order to prevent this, as shown in FIG. 3, the number of times of writing is distributed, in which data is written in an empty block and data in the physical block that is no longer needed is erased to make a new empty area. Means are also used in the present invention.

  That is, what is important is that the logical block is written back in the same part, but based on the logical / physical conversion table, the physical block is written in a part different from the original physical block.

  From the above, whether the read-only file or the rewrite file is not limited to the attribute, the rewrite frequency leveling algorithm is followed.

  Next, in order to realize the principle shown in FIGS. 2 and 3, the logical / physical conversion in which the physical block of the actual flash memory is associated with the logical block notified or responding from the host computer. The counter of the table is incremented by one (S4), and the same processing is repeated until the end logical block ELB is reached (S5).

  The effect obtained by using the means of the present invention will be described with reference to FIG. In comparison, in contrast to the defect that the read-only file is not the target of the number of rewrites in FIG. 8A, the read-only file is also leveled as shown in FIG. The erase / write count is averaged over the entire area.

In FIG. 8B , the number of times of erasing / writing in the rewrite file and the empty area slightly increases as compared to the read-only file because the physical block is rewritten after the OS starts up.
[Embodiment 2]
Secondly, the embodiment of the present invention is as follows. The basic configuration is the same as that of the first embodiment.
As a difference, in the first embodiment, all blocks from the logical start block SLB to the logical end block ELB are read / rewritten. In the second embodiment, however, this is not performed every time. Is an even logical block, and the next time after rebooting, the process is divided into an odd logical block.
[Embodiment 3]
Thirdly, the following is mentioned as an embodiment of the present invention. The basic configuration is the same as that of the first embodiment.
As a difference, in the first embodiment, all blocks from the logical start block SLB to the logical end block ELB are read and rewritten. In the third embodiment, however, this is not performed every time. Is divided into the first half of the logical block and the second half after the reboot.
[Embodiment 4]
Fourthly, the embodiment of the present invention is as follows. The basic configuration is the same as that of the first embodiment.
As a difference, in the first embodiment, all blocks are read / rewritten from the logical start block SLB to the logical end block ELB, but in the fourth embodiment, the BIOS is not subjected to the entire area every time. (Basic Input / Ou tp ut System ) as read date information from, it is conceivable to set whether to perform processing based thereon. For example, when booted on the first day of every month, the process is executed, but if it is not executed on the other day, the process is divided.

  By adopting any one of the embodiments 2 to 4 described above, the rewrite count leveling process is distributed, thereby enabling the OS to be started more quickly than in the first embodiment. Is also possible.

  From the above, the first effect of the present invention is that the entire area including the read-only file is the target of leveling of the number of rewrites, and as a result, the level of deterioration of the flash memory can be made uniform and the product life can be extended. Is a point.

  The second effect is that smoothing processing can be performed without being restricted by the OS or application software by performing the leveling processing of the number of rewrites before the OS boots.

It is a figure which shows the structural example of this invention. It is a figure which shows the example of the memory management system of a flash memory controller. It is a figure which shows the example of the leveling algorithm of the rewrite frequency. It is a figure which shows the example of the leveling algorithm of the rewrite frequency. It is a figure which shows the search direction of an empty physical block. It is a figure showing the relationship between the structure of a file, and the number of times of erasing / writing. It is a figure showing the relationship between the structure of a file, and the number of times of erasing / writing. It is a figure showing the relationship between the structure of a file, and the number of times of erasing / writing. It is a conceptual diagram showing the mechanism in which OS starts from a boot device. It is a conceptual diagram showing that the rewriting process is performed before OS starting by this invention. It is a flowchart showing the block unit and rewriting by this invention.

Explanation of symbols

10 Flash memory group 20 Flash memory controller 30 Host computer

Claims (10)

A flash memory drive device comprising a flash memory controller,
Logical block rewriting means for reading data from each logical block of the flash memory at boot time and writing the read data back to the same logical block as the logical block from which the read data was read;
A physical block changing means for writing data back to a physical block different from that at the time of reading when writing by the logical block writing;
Equipped with a,
The flash memory drive apparatus according to claim Rukoto to operate by dividing the rewrite means a plurality of times. A flash memory drive device comprising a flash memory controller,
Logical block rewriting means for reading data from each logical block of the flash memory at boot time and writing the read data back to the same logical block as the logical block from which the read data was read;
A physical block changing means for writing data back to a physical block different from that at the time of reading when writing by the logical block writing;
Means for reading date information from the BIOS ;
With
Flash memory drive apparatus according to claim and Turkey periodically operates the rewrite unit based on the date information. The flash memory drive device according to claim 1 or 2 ,
The flash memory drive device, wherein the logical block rewriting unit and the physical block changing unit operate before starting an OS loader. The flash memory drive device according to claim 1 or 2 ,
The physical block changing means includes
A flash memory drive device that operates based on a conversion table that holds a correspondence relationship between a logical block and a physical block. A method of controlling a flash memory drive device comprising a flash memory controller,
A logical block rewriting step of reading data from each logical block of the flash memory at the time of booting and writing the read data back to the same logical block as the logical block from which the read data was read;
A physical block changing step of writing data back to a physical block different from that at the time of reading when writing by the logical block writing ;
Equipped with a,
Control method of a flash memory drive apparatus according to claim Rukoto said rewriting step is performed by dividing into multiple times. A method of controlling a flash memory drive device comprising a flash memory controller,
A logical block rewriting step of reading data from each logical block of the flash memory at the time of booting and writing the read data back to the same logical block as the logical block from which the read data was read;
A physical block changing step of writing data back to a physical block different from that at the time of reading when writing by the logical block writing;
Reading date information from the BIOS ;
With
Control method of a flash memory drive apparatus characterized that you perform periodically the rewrite step based on the date information. A method for controlling a flash memory drive device according to claim 5 or 6,
A control method of a flash memory drive device, wherein the logical block rewriting step is performed before starting an OS loader. A method for controlling a flash memory drive device according to claim 5 or 6 ,
The physical block changing step includes:
A control method for a flash memory drive device, which is performed based on a conversion table that holds a correspondence relationship between a logical block and a physical block. Help program to perform the method according to any one of claims 5 to 8 on a computer. 10. A flash memory drive device, wherein the program of claim 9 is stored in an unallocated area of a flash memory.

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