CN111459409B - An optimized flash solid state disk heating method and flash solid state disk - Google Patents

Abstract

The invention discloses an optimized flash memory solid-state disk heating method and a flash memory solid-state disk, and belongs to the field of flash memory storage equipment. The method comprises the following steps: recording the average residence time DT of the end of the service life of each flash memory block in the flash memory solid-state disk_avgCalculating the actual reliability RBER of the flash memory block according to the average residence time of the flash memory block; comparing the RBER and CBER sizes of the flash blocks, according to DT_avgAdding the values into proper positions in the corresponding list in sequence; when the flash memory solid-state disk reaches the end of the service life, only the flash memory blocks in the flash memory block list with short residence time are heated, and the flash memory blocks in the flash memory block list with long residence time are not heated. According to the invention, by considering the influence of the average residence time of the flash memory block on the reliability recovery of the flash memory, a part of unnecessary high-delay and high-energy-consumption heating operation can be reduced under the condition of not influencing the reliability of the solid state disk, and the heating efficiency of the solid state disk is improved.

Description

An optimized flash solid state disk heating method and flash solid state disk

technical field

The invention belongs to the field of flash memory storage devices, and more particularly, relates to an optimized flash memory solid state disk heating method and a flash memory solid state disk.

Background technique

Flash solid-state disk is a non-volatile storage device that uses flash memory as a storage medium, and is widely used in computer storage systems. Flash SSDs have many different inherent characteristics compared to mechanical hard drives. For example, the read and write speed is asymmetric, the data is updated in different places, and the flash memory chip has a fixed number of erasing and writing (P/E). When the number of times of erasing and writing of the flash memory chips in the flash solid state disk reaches the preset threshold given by the manufacturer, the flash solid state disk cannot guarantee the validity of the stored data information, so the life of the flash solid state disk is reached.

In order to prolong the life of the flash solid state disk, a built-in heating device can be added to the flash solid state disk to realize the self-heating recovery technology. Through the flash memory chip structure with a built-in heating plate, the flash solid state disk can restore the storage capacity of the flash memory chip to a certain extent by heating, and prolong the life of the flash solid state disk. At the P/E threshold preset by the manufacturer, the flash solid state disk reaches the service life, and at this time, heating the failed flash memory block can increase an additional number of erasing and writing times.

Since the heating operation is time-consuming, for example, nearly one second, each time the heating is performed, the normal I/O read and write operations will be negatively affected, and the performance of the flash solid state disk will fluctuate. Furthermore, performing heating operations in these chip structures requires a sustained period of electrical and power consumption. Especially when a large number of heating operations are performed in a certain period of time, it will cause great performance fluctuations and increase energy consumption, so that a stable flash solid state disk cannot be realized.

SUMMARY OF THE INVENTION

In view of the problems of high delay and high energy consumption of the prior art heating method, the present invention provides an optimized flash memory solid state disk heating method and flash memory solid state disk, the purpose of which is to reduce unnecessary heating operations and improve the heating efficiency of solid state disks .

In order to achieve the above object, according to the first aspect of the present invention, an optimized flash memory solid state disk heating method is provided, and the method includes the following steps:

S1. Record the average residence time DT _avg at the end of the life of each flash block in the flash solid state disk, and calculate the actual reliability RBER of the flash block according to the average residence time of the flash block;

S2. Compare the actual reliability RBER of each flash memory block and the correctable bit error rate CBER of the built-in error correction code of the flash solid state disk. When RBER<CBER, add the flash memory block to the long residence time flash block list LDT ; Otherwise, add the flash block list SDT with short residence time; when adding to the list, add the appropriate position in the corresponding list in order according to the size of the DT _avg value;

S3. When the flash solid state disk reaches the end of its service life, the heating operation is only performed on the flash memory blocks in the flash memory block list with short residence time, and the heating operation is not performed on the flash memory blocks in the flash memory block list with long residence time.

Preferably, step S1 includes the following sub-steps:

S11. Track the current erasing times PE _current of the flash memory blocks in the healthy flash memory block list, and obtain the upper limit PE _limit of the erasing and writing times of the flash memory block, wherein PE _limit is initialized to the upper limit of erasing and writing times PE _init set by the manufacturer. When the PE _current of the flash block is equal to PE _limit -PE ^* , PE ^* is the number of times of erasing and writing that can affect the reliability recovery of the flash block, and the process goes to step S12;

S12. Record the residence time of the flash memory block between two erasing times of PE _limit -PE ^* and PE _limit -PE ^* +1

当该闪存块的PE_current＝PE_limit时，进入步骤S14；S13. Before the number of times of erasing and writing of the flash memory block reaches the PE _limit , circularly record the dwell time between two consecutive times of erasing and writing.

When PE _current =PE _limit of the flash memory block, go to step S14;

S14. Calculate the average residence time _DTavg of the flash memory block according to the multiple recorded residence times of the flash memory block;

S15. Calculate the actual reliability RBER of the flash memory block according to the average residence time DT _avg of the flash memory block.

Preferably, the calculation formula of the actual reliability RBER of the flash memory block is:

RBER=RBER _init +a*(PE _current +b)*ln(1+RT _max /(c+d*DT _avg ))

Among them, RBER _init is the original bit error rate when data programming is completed, PE _current is the current number of erasing and writing, RT _max is the time required by the manufacturer to maintain data after programming, DT _avg is the average residence time of the flash block, a , b, c, d are the four formula correlation coefficients.

Preferably, PE ^* is 20.

Preferably, step S3 includes the following sub-steps:

S31. When the flash solid state disk reaches the end of its service life, go to step S32;

S32. determine whether there is a flash memory block in the SDT, if so, select the flash memory block with the shortest residence time from the flash memory block list of the short residence time, enter step S33, otherwise, end;

S33. Perform a heating operation on the flash memory block, then delete the flash memory block from the SDT and put it into the healthy flash memory block list, and go to step S32.

In order to achieve the above object, according to the second aspect of the present invention, a flash solid state disk is provided, the flash solid state disk includes a control module, the control module adopts the optimized flash memory solid state disk heating method as described in the first aspect, and the heating fails. flash block.

Preferably, the data allocation of the flash solid state disk includes the following steps:

(1) If there is a healthy flash memory block in the flash solid state disk, select a flash memory block with the least number of heating times as the active flash memory block, and put the newly arrived data into the active flash memory block for storage; otherwise, go to step (2);

(2) If there is a flash block list LDT with a long residence time in the flash solid state disk, the flash block with the longest residence time is preferentially selected from the list as the active flash block. At this time, the number of erase and write cycles of the flash block is The upper limit PE _limit will increase PE(DT _avg ), where PE(DT _avg ) represents the increased number of erase/write cycles when the residence time is DT _avg , and the newly arrived data will be stored in the active flash memory block; otherwise, enter step (3);

(3) If there is a flash block list SDT with a short residence time in the flash solid state disk, the flash block with the shortest residence time is preferentially selected from the list as the active flash block. When the RBER of the flash block is greater than or equal to CBER, the first Perform a warm operation to place newly arrived data into active flash block storage.

In general, through the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

(1) In view of the traditional heating method, when the flash solid state disk fails, a large number of flash memory block heating operations are performed in a short time, and excessive heating operations lead to long heating time and high energy consumption. When the end of the service life is reached, the flash block in the flash block list with short residence time will be preferentially heated, and the flash block in the flash block list with long residence time will not be heated, and the average residence time of the flash block will be considered. The impact on the reliability recovery of the flash memory can reduce some unnecessary high-latency and high-energy-consuming heating operations without affecting the reliability of the solid-state drive, and improve the heating efficiency of the solid-state drive.

(2) In view of the fact that the traditional data allocation strategy does not consider the problem of flash memory blocks that do not need to perform heating operations, the present invention solves the problem of data allocation after the optimized flash solid state disk heating method by enhancing the priority of allocating flash memory blocks during data allocation .

Description of drawings

FIG. 1 is a flowchart of an optimized flash solid state disk heating method provided by an embodiment of the present invention;

FIG. 2 is a schematic diagram of an improved data allocation provided by an embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as there is no conflict with each other.

First, the terms involved in the present invention are explained as follows:

Flash block residence time: The time between two consecutive erase and write cycles of a flash block.

As shown in FIG. 1 , the present invention provides an optimized flash solid state disk heating method, which includes the following steps:

Step S1. Record the average residence time DT _avg at the end of life of each flash block in the flash solid state disk, and calculate the actual reliability RBER of the flash block according to the average residence time of the flash block.

Step S1 includes the following sub-steps:

S11. Track the current erasing times PE _current of the flash memory blocks in the healthy flash memory block list, and obtain the upper limit PE _limit of the erasing and writing times of the flash memory block, wherein PE _limit is initialized to the upper limit of erasing and writing times PE _init set by the manufacturer. When the PE _current of the flash memory block is equal to PE _limit -PE ^* , PE ^* represents the number of times of erasing and writing that can affect the reliability recovery of the flash memory block, and the process proceeds to step S12.

The flash blocks in the healthy flash block list are initialized to all flash blocks in the flash solid state disk. As processing progresses, some flash blocks are added to the long-duration flash block list LDT or the short-duration flash block list SDT.

The value of PE* ranges from 1 to PE _init , and is preferably 20 in this embodiment.

S12. Record the residence time of the flash memory block between two erasing times of PE _limit -PE ^* and PE _limit -PE ^* +1

When the PE _current of the flash block is equal to PE _limit -20, the controller of the flash solid state disk records the start time T ₁ at which the flash block is allocated as an active block to store newly arrived data. When the PE _current of the flash block is equal to PE _limit -19, the controller of the flash solid state disk records the start time T ₂ at which the flash block is allocated as an active block to store newly arrived data. Based on the above two times, the dwell time DT ₂₀ =T ₂ -T ₁ is calculated.

当该闪存块的PE_current＝PE_limit时，进入步骤S14。S13. Before the number of times of erasing and writing of the flash memory block reaches the PE _limit , circularly record the dwell time between two consecutive times of erasing and writing.

When the PE _current of the flash block is equal to PE _limit , the process proceeds to step S14.

Calculate the dwell time between PE _{limit -19} and PE _limit -18, PE _{limit -18} and PE _limit -17...PE _limit -1 and PE _limit respectively .DT ₁ .

S14. Calculate the average residence time _DTavg of the flash memory block according to the multiple recorded residence times of the flash memory block.

S15. Calculate the actual reliability RBER of the flash memory block according to the average residence time DT _avg of the flash memory block.

The formula for calculating the actual reliability RBER of a flash block is:

RBER=RBER _init +a*(PE _current +b)*ln(1+RT _max /(c+d*DT _avg ))

Among them, RBER _init is the original bit error rate when data programming is completed, PE _current is the current number of erasing and writing, RT _max is the time required by the manufacturer to maintain the data after programming, DT _avg is the average residence time of the flash block, a , b, c, d are the four formula correlation coefficients.

Step S2. Compare the actual reliability RBER of each flash memory block with the size of the correctable bit error rate CBER of the built-in error correction code of the flash solid state disk. When RBER<CBER, add the flash memory block to the list of flash memory blocks with a long residence time LDT; otherwise, add the flash memory block list SDT with short residence time; when adding the corresponding list, add it to the appropriate position in the corresponding list in order according to the size of the DT _avg value.

The longer the residence time is, the more the reliability of the flash memory can be recovered. Therefore, the present invention focuses on heating and recovering the flash memory block with a short residence time. The long-duration flash block list LDT and the short-duration flash block list SDT are initialized to be empty.

Step S3. When the flash solid state disk reaches the end of its service life, the heating operation is only performed on the flash memory blocks in the flash memory block list with short residence time, and the heating operation is not performed on the flash memory blocks in the flash memory block list with long residence time.

S31. When the flash solid state disk reaches the end of its service life, go to step S32.

In the present invention, the criterion for judging that the flash memory solid state disk reaches the end of its service life is that 80% of the flash memory blocks fail. When the flash SSD reaches the end of its life, due to the wear leveling strategy, the PE _current of most flash blocks reaches the PE _limit . At this time, the flash memory block with the shortest residence time is preferentially selected from the SDT to determine whether to perform the heating operation.

S32. Determine whether there is a flash memory block in the SDT, if yes, select the flash memory block with the shortest residence time from the list of flash memory blocks with short residence time, and proceed to step S33, otherwise, end.

The next flash memory block with the shortest residence time is cyclically selected from the SDT for heating determination until all the flash memory blocks in the SDT are detected.

S33. Perform a heating operation on the flash memory block, then delete the flash memory block from the SDT and put it into the healthy flash memory block list, and go to step S32.

At this time, the upper limit PE _limit of the number of erasing and writing cycles of the flash memory block will be increased by PE _i , where PE _i represents the number of erasing and writing cycles increased after the i-th heating.

The present invention also provides a flash memory solid state disk, the flash memory solid state disk includes a control module, and the control module adopts the above optimized flash memory solid state disk heating method to heat the failed flash memory blocks.

As shown in Figure 2, the data allocation of the flash solid state disk includes the following steps:

(1) If there is a "healthy" flash block in the flash SSD, select a flash block with the least number of heating times as the "active" flash block, and store the newly arrived data in the active flash block; otherwise, go to step (2) );

(2) If there is a flash block list LDT with a long residence time in the flash solid state disk, the flash block with the longest residence time is preferentially selected from the list as the "active" flash block. At this time, the flash memory block is erased and written. The upper limit of cycle times, PE _limit , will increase PE(DT _avg ), where PE(DT _avg ) represents the increased number of erase/write cycles when the residence time is DT _avg , and the newly arrived data will be stored in the active flash memory block; otherwise , enter step (3);

(3) If there is a flash block list SDT with short residence time in the flash solid state disk, the flash block with the shortest residence time is preferentially selected from the list as the "active" flash block. When the RBER of the flash block is greater than or equal to CBER, A warm-up operation needs to be performed first to put the newly arrived data into the active flash block storage.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (5)

1. An optimized flash memory solid state disk heating method is characterized by comprising the following steps:

s1, recording average residence time DT of each flash memory block in flash memory solid-state disk_avgCalculating the actual reliability RBER of the flash memory block according to the average residence time of the flash memory block, and comprising the following substeps;

s11, tracking current erasing and writing times PE of flash memory blocks in healthy flash memory block list_currentObtaining the upper limit PE of the erasing times of the flash memory block_limitWherein, PE_limitInitialization as manufacturer-defined upper limit of erase-write times PE_initWhen a PE of a flash block_current＝PE_limit-PE^*When, PE^*If it is the number of times of erasing that can affect the reliability recovery of the flash memory block, the process proceeds to step S12;

s12, recording the flash memory block in PE_limit-PE^*And PE_limit-PE^*+1 dwell time DT between two erase counts_PE*；

S13, when the erasing frequency of the flash memory block reaches PE_limitBefore, the dwell time DT between two continuous erasing times is recorded in a circulating way_PE*-1,......,DT₁When the PE of the flash block_current＝PE_limitThen, the process proceeds to step S14;

s14, calculating the average residence time DT of the flash memory block according to the plurality of recorded residence times of the flash memory block_avg；

S15, according to the average residence time DT of the flash memory blocks_avgCalculating the actual reliability RBER of the flash memory block;

RBER＝RBER_init+a*(PE_current+b)*ln(1+RT_max/(c+d*DT_avg))

wherein, RBER_initIs the raw bit error rate, PE, at the completion of the data programming_currentIs the current erase-write times, RT_maxIs the time required to be maintained after the data programming, DT, required by the manufacturer_avgIs the average residence time of the flash memory block, and a, b, c, d are the correlation coefficients of four formulas;

s2, comparing the actual reliability RBER of each flash block with the correctable bit error rate CBER of the built-in error correcting code of the flash solid-state disk, and when the RBER is used, comparing the actual reliability RBER of each flash block with the correctable bit error rate CBER of the built-in error correcting code of the flash solid-state disk<When CBER is used, the flash memory block is added into a flash memory block list LDT with long residence time; otherwise, adding a flash memory block list SDT with short residence time; when joining the list, according to DT_avgThe size of the value is sequentially added to the corresponding list;

and S3, when the flash memory solid-state disk reaches the service life end, only heating the flash memory blocks in the flash memory block list with short residence time, and not heating the flash memory blocks in the flash memory block list with long residence time.

2. The method of claim 1, wherein PE is characterized in that^*Is 20.

3. The method according to claim 1 or 2, characterized in that step S3 comprises the sub-steps of:

s31, when the flash memory solid-state disk reaches the service life end, the step S32 is carried out;

s32, judging whether the SDT has a flash memory block, if so, selecting the flash memory block with the shortest residence time from a flash memory block list with short residence time, and entering the step S33, otherwise, ending;

s33, heating the flash memory block once, then deleting the flash memory block from the SDT and putting the flash memory block into a healthy flash memory block list, and entering the step S32.

4. A flash memory solid state disk, characterized in that it comprises a control module, which heats failed flash memory blocks using the optimized flash memory solid state disk heating method as claimed in any one of claims 1 to 3.

5. The flash memory solid state disk of claim 4, wherein the data allocation of the flash memory solid state disk comprises the steps of:

(1) if healthy flash memory blocks exist in the flash memory solid-state disk, selecting one flash memory block with the least heating times as an active flash memory block, and putting newly arrived data into the active flash memory block for storage; otherwise, entering the step (2);

(2) if a flash memory block list LDT with long residence time exists in the flash memory solid-state disk, selecting the flash memory block with the longest residence time from the list as an active flash memory block, and at the moment, the upper limit PE of the erasing cycle times of the flash memory block_limitWill increase PE (DT)_avg) Wherein, PE (DT)_avg) Denotes a dwell time of DT_avgUnder the condition of increased erasing and writing cycle times, newly arrived data is put into an active flash memory block for storage; otherwise, entering the step (3);

(3) if a flash memory block list SDT with short residence time exists in the flash memory solid-state disk, selecting the flash memory block with the shortest residence time from the list as an active flash memory block, and when the RBER of the flash memory block is more than or equal to CBER, firstly executing a heating operation, and putting newly arrived data into the active flash memory block for storage.

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