Bug 252384 - cmirror resync slows down when I/O is outstanding to the mirror
cmirror resync slows down when I/O is outstanding to the mirror
Product: Red Hat Cluster Suite
Classification: Red Hat
Component: cmirror (Show other bugs)
All Linux
medium Severity medium
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Assigned To: Jonathan Earl Brassow
Cluster QE
Depends On:
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Reported: 2007-08-15 14:14 EDT by Nate Straz
Modified: 2013-09-23 11:31 EDT (History)
7 users (show)

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Doc Type: Bug Fix
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Last Closed: 2013-09-23 11:31:26 EDT
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Description Nate Straz 2007-08-15 14:14:47 EDT
Cloning off the piece about performance of mirror resync dropping.

+++ This bug was initially created as a clone of Bug #252007 +++

Description of problem:

-- Additional comment from nstraz@redhat.com on 2007-08-13 15:40 EST --
We've run into similar problems with a fresh syncing mirror.  When we do a mkfs
on a not-yet-synced mirror, the mirror sync performance drops.  I did a quick
test now and found that on a 100G mirror with 3 legs (lvcreate -m 2), sync
performance was about 0.9% completion per minute.  After starting a mkfs -t gfs
(which hangs) mirror completion drops to 0.05% per minute.

-- Additional comment from jbrassow@redhat.com on 2007-08-13 15:46 EST --
Cluster mirrors in 4.5 did not have a way to coordinate device resyncing and
nominal I/O.  Therefore, nominal I/O had to be deferred until the regions were
resync'ed - causing excessive delay.  This has been addressed in 4.6.  See bug
Comment 1 Jonathan Earl Brassow 2007-09-28 11:28:00 EDT
The latest build in 4.6 (>= 9/28/07).  Addresses some of these concerns.  I was
forced to trade consistency for speed, however.  So, things will be faster than
4.5, but I'd like to know what the limitations are.

assigned -> needinfo
Comment 2 Jonathan Earl Brassow 2008-04-02 15:03:13 EDT
needinfo -> assigned

I have a patch ready, but it still needs to be tested.  I borrowed some ideas
from the rhel5 code, which I am using to limit the network traffic while there
is recovery + nominal I/O happening.

Perhaps this patch could make 4.8.
Comment 5 Lon Hohberger 2013-09-23 11:31:26 EDT
The Red Hat Cluster Suite product is past end-of-life; closing.

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