[Bugs] [Bug 1293534] guest paused due to IO error from gluster based storage doesn't resume automatically or manually
bugzilla at redhat.com
bugzilla at redhat.com
Tue Feb 16 09:13:50 UTC 2016
--- Comment #9 from Vijay Bellur <vbellur at redhat.com> ---
COMMIT: http://review.gluster.org/13057 committed in release-3.7 by Raghavendra
G (rgowdapp at redhat.com)
Author: Raghavendra G <rgowdapp at redhat.com>
Date: Tue Nov 17 12:57:54 2015 +0530
performance/write-behind: retry "failed syncs to backend"
1. When sync fails, the cached-write is still preserved unless there
is a flush/fsync waiting on it.
2. When a sync fails and there is a flush/fsync waiting on the
cached-write, the cache is thrown away and no further retries will
be made. In other words flush/fsync act as barriers for all the
previous writes. The behaviour of fsync acting as a barrier is
controlled by an option (see below for details). All previous
writes are either successfully synced to backend or forgotten in
case of an error. Without such barrier fop (especially flush which
is issued prior to a close), we end up retrying for ever even after
fd is closed.
3. If a fop is waiting on cached-write and syncing to backend fails,
the waiting fop is failed.
4. sync failures when no fop is waiting are ignored and are not
propagated to application. For eg.,
a. first attempt of sync of a cached-write w1 fails
b. second attempt of sync of w1 succeeds
If there are no fops dependent on w1 are issued b/w a and b,
application won't know about failure encountered in a.
5. The effect of repeated sync failures is that, there will be no
cache for future writes and they cannot be written behind.
fsync as a barrier and resync of cached writes post fsync failure:
Whether to keep retrying failed syncs post fsync is controlled by an
option "resync-failed-syncs-after-fsync". By default, this option is
set to "off".
If sync of "cached-writes issued before fsync" (to backend) fails,
this option configures whether to retry syncing them after fsync or
forget them. If set to on, cached-writes are retried till a "flush"
fop (or a successful sync) on sync failures. fsync itself is failed
irrespective of the value of this option, when there is a sync failure
of any cached-writes issued before fsync.
Signed-off-by: Raghavendra G <rgowdapp at redhat.com>
Signed-off-by: Raghavendra Talur <rtalur at redhat.com>
Smoke: Gluster Build System <jenkins at build.gluster.com>
NetBSD-regression: NetBSD Build System <jenkins at build.gluster.org>
CentOS-regression: Gluster Build System <jenkins at build.gluster.com>
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