<html><head></head><body bgcolor="#FFFFFF"><div>There is actually work well underway to add metadata checksums for ext4 into the upstream kernel.</div><div><br></div><div>This is using both inline and out-of-band locations to store the block checksum for the different metadata block types. The checksums on disk are crc32c. </div><div><br></div><div>Cheers, Andreas</div><div><br>On 2012-04-24, at 14:03, Johann Lombardi <<a href="mailto:johann@whamcloud.com">johann@whamcloud.com</a>> wrote:<br><br></div><div></div><blockquote type="cite"><div><div class="gmail_extra">On Sun, Apr 22, 2012 at 5:36 AM, Alexey Lyashkov <span dir="ltr"><<a href="mailto:alexey_lyashkov@xyratex.com" target="_blank">alexey_lyashkov@xyratex.com</a>></span> wrote:<div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word"><div>Why not? HCA provide a T10 checksumming when obdfilter (osd) submit a IO request - so it's before a call bio_done() function and before send a reply to client.<br>
</div></div></blockquote><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="word-wrap:break-word"><div>so we may don't want a commit as HCA verify a checksum and it's correct.</div>
</div></blockquote><div><br>I was actually concerned by checksum errors when committing metadata blocks to disk. That said, i assume that the low level driver is supposed to resubmit the I/O several times (ideally via multipath) on checksum errors and ultimately triggers a failover (to replay the I/O), right?<br>
<br>Cheers,<br>Johann<br></div></div></div>
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