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Date:      Sun, 22 Aug 2010 18:26:40 +0200
From:      Martin Matuska <mm@FreeBSD.org>
To:        Olivier Smedts <olivier@gid0.org>
Cc:        freebsd-current@freebsd.org
Subject:   Re: [CFT] Improved ZFS metaslab code (faster write speed)
Message-ID:  <4C714FC0.90005@FreeBSD.org>
In-Reply-To: <AANLkTi=8x1EenWyqGz6AQWKDUq5JiMJbX_jbVbX43DKx@mail.gmail.com>
References:  <4C713EF5.8080402@FreeBSD.org> <AANLkTi=8x1EenWyqGz6AQWKDUq5JiMJbX_jbVbX43DKx@mail.gmail.com>

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 Thank you, I have updated the v15 patch for 8-STABLE.

Dňa 22. 8. 2010 17:44, Olivier Smedts wrote / napísal(a):
> 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 patch:
>> http://people.freebsd.org/~mm/patches/zfs/zfs_metaslab.patch
>>
>> To apply the patch against 8-STABLE, you need to apply the v15 update first:
>> 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 aoû 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=8270
>> [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
>> _______________________________________________
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>>
>
>



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