Bug 252384

Summary:	cmirror resync slows down when I/O is outstanding to the mirror
Product:	[Retired] Red Hat Cluster Suite	Reporter:	Nate Straz <nstraz>
Component:	cmirror	Assignee:	Jonathan Earl Brassow <jbrassow>
Status:	CLOSED DEFERRED	QA Contact:	Cluster QE <mspqa-list>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	4	CC:	agk, cfeist, dwysocha, iannis, jbrassow, prockai, pvrabec
Target Milestone:	---
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Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
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Clone Of:		Environment:
Last Closed:	2013-09-23 15:31:26 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Nate Straz 2007-08-15 18:14:47 UTC

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 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 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
238629.

Comment 1 Jonathan Earl Brassow 2007-09-28 15:28:00 UTC

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 19:03:13 UTC

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 15:31:26 UTC

The Red Hat Cluster Suite product is past end-of-life; closing.