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<DIV><FONT face=Arial size=2>Hi Johann!</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>The original design does not cover metadata
integrity. Guard tag value 0xffff can be used to avoid guard tag integrity
checks on specific (metadata) sectors.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>If metadata is to be included in integrity
checks, then I/O replay should be implemented for recoverable errors. Since
T10 tag mismatches don't seem to be</FONT></DIV>
<DIV><FONT face=Arial size=2>the only </FONT><FONT face=Arial size=2>possible
source of recoverable errors, this looks like an existing defect in current
BRW RPC handling/async_journal implementation (?).</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Andrew</FONT></DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=johann@whamcloud.com href="mailto:johann@whamcloud.com">Johann
Lombardi</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=alexey_lyashkov@xyratex.com
href="mailto:alexey_lyashkov@xyratex.com">Alexey Lyashkov</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Cc:</B> <A title=carrier@cray.com
href="mailto:carrier@cray.com">John Carrier</A> ; <A
title=twg@lists.opensfs.org
href="mailto:twg@lists.opensfs.org">twg@lists.opensfs.org</A> ; <A
title=discuss@lists.opensfs.org
href="mailto:discuss@lists.opensfs.org">discuss@lists.opensfs.org</A> ; <A
title=Andrew_Perepechko@xyratex.com
href="mailto:Andrew_Perepechko@xyratex.com">AndrewPerepechko</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, April 24, 2012 10:03
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Discuss] [Twg] T10
End-to-End Data Integrity HLD</DIV>
<DIV><BR></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>
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style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">
<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="PADDING-LEFT: 1ex; MARGIN: 0pt 0pt 0pt 0.8ex; BORDER-LEFT: rgb(204,204,204) 1px solid">
<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></BLOCKQUOTE></BODY></HTML>