On 08/17/2017 08:03 PM, Shaohua Li wrote:
On Wed, Aug 16, 2017 at 05:13:44PM +0200, Pawel Baldysiak wrote:
Current Partial Parity Log implementation allows only single PPL to be
written to particular member drive. In such case PPL entry is
overwritten by every write as it's stored at the same sector of a drive.
Such approach is suboptimal for SSD drives as it leads to increased
write amplification factor due to write-after-write limitations.
This patchset changes the implementation by extending PPL area to 1MB.
PPL is not stored at fixed location but multiple PPLs are written in a
circular buffer. There is at most one valid PPL at any time (latest
one). Recovery algorithm stays the same. The main benefits of this
approach are increased drive lifespan and in some cases improved
performance.
The patches look good. Is this in intel RST standard?
Hello,
Yes, this is a part of upcoming RSTe version.
I didn't get the point why this is helpful though. You mentioned reduce write
amplification. Why does this reduce write amplification? As far as I know, SSD
never does in-place write, write to the same sector or different sector has no
difference.
Well, it depends on SSD drive and firmware implementation.
Thanks,
Pawel
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