Date: Sun, 22 Aug 2010 17:44:52 +0200 From: Olivier Smedts <olivier@gid0.org> To: Martin Matuska <mm@freebsd.org> Cc: freebsd-current@freebsd.org Subject: Re: [CFT] Improved ZFS metaslab code (faster write speed) Message-ID: <AANLkTi=8x1EenWyqGz6AQWKDUq5JiMJbX_jbVbX43DKx@mail.gmail.com> In-Reply-To: <4C713EF5.8080402@FreeBSD.org> References: <4C713EF5.8080402@FreeBSD.org>
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2010/8/22 Martin Matuska <mm@freebsd.org>: > Dear FreeBSD community, > > many of our [2] (and Solaris [3]) users today are complaining about slow > ZFS writes. One of the causes for these writes is the selection of the > proper allocation method for allocation of new blocks [3] [4]. Another > issue a write slowdown during TXG sync times. > > Solaris 10 (and OpenSolaris up to november 2009) have the > following scenario: > > - pool has more than 30% free space: use first fit method [1] > - pool has less than 30% free space: use best fit method [1] > > This causes a major slowdown of the writes if we go below 30% of free > space. On large pools, 30% may be terabytes of free space. > > OpenSolaris has changed this in November 2009 and the Oracle Storage > Appliances also included the new code in Q1/2010 [1]. > > The source [1] states, that with this change they archieved a speedup > of: "50% Improved OLTP Performance, 70% Reduced Variability, 200% > Improvement on MS Exchange" > > I would like to issue a Call For Testing for the following 9-CURRENT patc= h: > http://people.freebsd.org/~mm/patches/zfs/zfs_metaslab.patch > > To apply the patch against 8-STABLE, you need to apply the v15 update fir= st: > http://people.freebsd.org/~mm/patches/zfs/v15/stable-8-v15.patch This one doesn't apply cleanly since few minutes : # svn log -l 1 sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c ------------------------------------------------------------------------ r211599 | avg | 2010-08-22 10:18:32 +0200 (Dim 22 ao=FB 2010) | 7 lignes Fix a mismerge in r211581, MFC of r210427 This is a direct commit. Reported by: many Pointyhat to: avg ------------------------------------------------------------------------ But it does not seem hard to correct. Do you want me to submit an updated patch for 8-stable ? > The patch includes the following OpenSolaris onnv revisions: > 10921 (partial), 11146, 11728, 12047 > > And covers the following Bug IDs: > 6826241 Sync write IOPS drops dramatically during TXG sync > 6869229 zfs should switch to shiny new metaslabs more frequently > 6917066 zfs block picking can be improved > 6918420 zdb -m has issues printing metaslab statistics > > References: > [1] http://blogs.sun.com/roch/entry/doubling_exchange_performance > [2] http://forums.freebsd.org/showthread.php?t=3D8270 > [3] > http://blogs.everycity.co.uk/alasdair/2010/07/zfs-runs-really-slowly-when= -free-disk-usage-goes-above-80/ > [4] http://blogs.sun.com/bonwick/entry/zfs_block_allocation > [5] http://blogs.sun.com/bonwick/entry/space_maps > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org= " > --=20 Olivier Smedts=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 = =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=A0 _ =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0= =A0 ASCII ribbon campaign ( ) e-mail: olivier@gid0.org=A0 =A0 =A0 =A0 - against HTML email & vCards=A0 X www: http://www.gid0.org=A0 =A0 - against proprietary attachments / \ =A0 "Il y a seulement 10 sortes de gens dans le monde : =A0 ceux qui comprennent le binaire, =A0 et ceux qui ne le comprennent pas."
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