[Twg] T10 End-to-End Data Integrity HLD

[Alexey Lyashkov]

On Apr 20, 2012, at 08:41, Andreas Dilger wrote:

> On 2012-04-19, at 11:57, Alexey Lyashkov <alexey_lyashkov at xyratex.com> wrote:
>> On Apr 19, 2012, at 01:55, Andreas Dilger wrote:
>>> 
>>> Based on the data in LU-1201, I think with Nehalem CPUs and multi-threaded ptlrpcd the checksum overhead will become a non-issue, and people will happily leave it enabled all the time.  The unfortunate thing is that the CRC16 used by T10-DIF has such poor software performance that I agree there is no option but to leave the verification to the hardware.
>>> 
>> Based on Xyratex test results - crc32c HW implementation isn't best choose, and multi thread ptlrpcd isn't help to improve a  OST side loading.
>> yes, main problem is OST side, not a client side checksumming.
>> 
>> Typical speed is less 1Gb/s for crc32c hw, and it's less speed then adler may provide.
>> Current top speed list - adler, crc32 hw based on (not crc32c), crc32c hw, both crc32c table implementation.
> 
> I think we both agree in any case that the current crc16-t10dif is not nearly as fast as any of these 32-bit checksums. This may prove to be a major discouragement to using T10-PI even if it is available. 
> 
per Xyratex internal discussion, we can use same way as crc32 improvement to provide crc16 speed up, so it`s should be have speed near of 2Gb/s.