From: NeilBrown <neilb@suse.com>
To: Peter Sangas <pete@wnsdev.com>,
'Stephane Thiell' <sthiell@stanford.edu>,
linux-raid@vger.kernel.org
Subject: RE: mismatch_cnt > 0 during initial sync?
Date: Wed, 21 Jun 2017 07:26:11 +1000 [thread overview]
Message-ID: <87bmpi2vws.fsf@notabene.neil.brown.name> (raw)
In-Reply-To: <002e01d2ea03$232cb660$69862320$@wnsdev.com>
[-- Attachment #1: Type: text/plain, Size: 1237 bytes --]
On Tue, Jun 20 2017, Peter Sangas wrote:
>> From: NeilBrown [mailto:neilb@suse.com]
>> Sent: Monday, June 19, 2017 9:15 PM
>> Subject: RE: mismatch_cnt > 0 during initial sync?
>>
>> This is a recovery, not a resync. They are different.
>
> Thank you for pointing this out and the nice explanation.
>
> From reading this list and other sources issuing a repair command as
> follows:
>
> "echo repair > /sys/block/md2/md/sync_action"
>
> might be ill-advised since it's luck of the draw whether or not the
> operation gets the right data instead of the bad data.
>
> Is this correct?
How do you define "right data" and "bad data"?
What is your threat-model which explains how the two blocks are
different?
In most likely cases, neither version if the data is more correct than
the other. In some others, your hardware is broken and needs to be
replaced.
If you have no understanding of why there might be a difference, then
issuing a repair is not likely to be worse than not issuing a repair.
If you do have that understanding, then use that to make your decision.
NeilBrown
>
> For reference I have a RAID1 with 3 disks. mdadm - v3.3 - 3rd September
> 2013
>
> Thank you,
> Pete
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 832 bytes --]
prev parent reply other threads:[~2017-06-20 21:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-24 22:01 mismatch_cnt > 0 during initial sync? Stephane Thiell
2017-04-25 5:14 ` Stephane Thiell
2017-06-16 17:28 ` Peter Sangas
2017-06-18 21:34 ` NeilBrown
2017-06-19 21:54 ` Peter Sangas
2017-06-20 4:14 ` NeilBrown
2017-06-20 20:23 ` Peter Sangas
2017-06-20 21:26 ` NeilBrown [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87bmpi2vws.fsf@notabene.neil.brown.name \
--to=neilb@suse.com \
--cc=linux-raid@vger.kernel.org \
--cc=pete@wnsdev.com \
--cc=sthiell@stanford.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).