Test Principle as well as Key Things of SSD Power - Down Defense


Solid-state disk drive If you have to utilize FTL to do the sensible address and the physical address in between the conversion, if the SSD read, create, remove as well as various other typical work in the case of irregular power-down, may create mapping table because of far too late to upgrade and shed There is a mistake that the SSD can not be acknowledged by the system.

At the same time, in order to improve read and also write efficiency, usually utilize SDRAM to do the cache, if the process of analysis and also writing encountered abnormal power-down, SDRAM information may be far too late to write Nand Flash data loss, or upgrade the mapping table too late to write Nand Flash The mapping table is missing.

Abnormal power failing brought on by the sensation

SSD unusual power failing generally there are three sort of failing sensation:

1, SSD can not reproduce the system recognition, the requirement to restore the mapping table or by basic and crude way to re-production can be used;

2, many times after power failure, SSD there are a lot of “new poor block”;

The system behind the new bad block is that when the SSD checks out, creates, or removes unsuccessfully, it will be recognized as a negative block. Naturally, these blocks are not actually negative blocks, just because they are irregular Power failure brought on by the wrong judgment.

3, SDRAM information loss;

Common power-down defense device

Each power-down security mechanism to recognize various, various for the user, the protection device is entirely different, typically there will certainly be the complying with two methods:

1, save all the data in SDRAM

Unusual power-down, SDRAM all information should be totally contacted Nand Flash, as a whole, SDRAM capacity is set to 1000% of the quantity of SSD bare capacity, for tiny capacity SSD, SDRAM need to create Nand Flash information Relatively small, via the extremely capacitor or tantalum capacitor can remain to compose information. Nonetheless, if the SSD capability is large sufficient, for instance: 8TB, after that, SDRAM need to compose Nand Flash data will certainly be large, if still rely upon very capacitor or tantalum capacitor to do power supply, will certainly face the adhering to three complicated problem:

a, the demand for even more tantalum capacitor fragments to do the defense, in the actual design practice, this is a really serious examination, the designers encounter the thickness, the common dimension limitation, PCB area is not enough to utilize;

b, also if there is enough capacitance to do the protection, when the application of the “restart”, the SSD will certainly not start effectively, you must initially close down for a long time before rebooting, because: SSD demand to place all the tantalum capacitor after power Determined;

c, when the use of a few years after the tantalum capacitor or incredibly capacitor after aging, when the tantalum capacitor power supply can not attain the first style target worth, the user still has data loss after power loss or SSD can not recognize the potential risks, if the initial design That is, to do redundant capacitors, after that, will return to the problem “b” fatality cycle.

It is gratifying that the troubles of b and also c are best services to resolve these tough issues just require the designers sufficient mind and also experience only.

2, only conserve the SDRAM customer information, without conserving the mapping table

This will certainly decrease using SDRAM as well as making use of tantalum capacitors, “do not save the mapping table” does not imply that the mapping table is lost, just do not conserve the last information compose upgrade map, when the SSD re-power, Seeking the last mapping table to conserve the brand-new data written to re-build the mapping table, the drawbacks of this approach is inadequate system to set the affordable, after that rebuild the mapping table will certainly be longer, SSD takes some time to regular access to typical

For controllers without SDRAM layout, all data is written directly to Nand Flash. When information is lost, the data that is not contacted Nand Flash will be gone back to the host. If no added data requires to be saved, High integrity requirements of the application, no SDRAM design is king, its agent is a German commercial brand name master, its only disadvantage is that the efficiency is unsatisfactory, actually, many applications and the need for the highest possible performance, and also Is “sufficient” performance.

Examination approaches and also concepts

Specific examination, SSD need as a system disk and also as a disk from both cases of screening, so the main disk and also do from the disk test approach is the only distinction is that the primary disk need to evaluate the computer to power off the device, and from the disk only SSD can be on the power off.

a, respectively, of the SSD as an empty disc, data is composed in the 25% as well as 50% when writing data, the create information for 85% and also 3000, specifically, the unusual power down 100% examination compose data, each down And also the power-on time interval of 3 seconds;

The principle of composing various capacity information to the disk is: When the SSD compose a particular quantity of data, the history began to garbage collection, garbage collection means that the moving of information, information migration means that the mapping table updates, at this time Irregular power failure is usually an issue.

b, when the regular write data, the SSD unusual power-down

c, when the data is deleted when the irregular power-down

In the home windows, delete the information also require to do 8 actions, and the establishment of the same document, the mapping table likewise need to update.

d, when the SSD checked out documents is abnormal power down, examination 3000 times, power off time period of 3 seconds;

e, when the typical closure process abnormal power down, test 3000 times;

f, when the regular start of the operating system irregular power down, test 3000 times;