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Date:      Wed, 20 Jan 2010 01:03:41 +0100
From:      "O. Hartmann" <ohartman@mail.zedat.fu-berlin.de>
To:        =?UTF-8?B?TW9yZ2FuIFdlc3N0csO2bQ==?= <freebsd-questions@pp.dyndns.biz>
Cc:        FreeBSD Stable <freebsd-stable@freebsd.org>, freebsd-questions@freebsd.org
Subject:   Re: immense delayed write to file system (ZFS and UFS2), performance issues
Message-ID:  <4B56485D.2010303@mail.zedat.fu-berlin.de>
In-Reply-To: <4B54C5EE.5070305@pp.dyndns.biz>
References:  <4B54C100.9080906@mail.zedat.fu-berlin.de> <4B54C5EE.5070305@pp.dyndns.biz>

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On 01/18/10 21:34, =EF=BF=BD wrote:
> O. Hartmann wrote:
>> I realise a strange behaviour of several FreeBSD 8.0-STABLE/amd64 boxe=
s.
>> All boxes have the most recent STABLE. One box is a UP system, two
>> others SMP boxes, one with a Q6600 4-core, another XEON with 2x 4-core=
s
>> (Dell Poweredge III).
>>
>> Symptome: All boxes have ZFS and UFS2 filesystems. Since two weeks or
>> so, sometimes the I/O performance drops massively when doing 'svn
>> update', 'make world' or even 'make kernel'. It doesn't matter what
>> memory and how many cpu the box has, it get stuck for several seconds
>> and freezing. On the UP box, this is sometimes for 10 - 20 seconds.
>> A very interesting phenomenon is the massively delayed file writing on=

>> ZFS filesystems I realise. Editing a file in 'vi' running on one XTerm=

>> and having in another Xterminal my shell for compiling this file, it
>> takes sometimes up to 20 seconds to get the file updated after it has
>> been written. It's like having an old, slow NFS connection with long
>> cache delays.
>> These massively delayed file transactions are not necessarely under
>> heavy load, sometimes they occur in a relaxed situation. They seem to
>> occur much more often on the UP box than on the SMP boxes, but this
>> strange phenomenon also occur on the Dell Poweredge II, which has 16GB=

>> RAM and summa summarum 16 cores. This phenomenon does occur on ZFS- an=
d
>> UFS2 filesystems as well. It is hardly reproducable.
>>
>> Is there any known issue?
>>
>> Ragrds,
>> Oliver
>
>
> The disks involved don't happen to be Western Digital Green Power disks=
,
> do they? The Intelli-Park function in these disks are wrecking havoc
> with I/O in Linux-land at least, causing massive stalls and iowait
> through the roof during the 25-30 seconds it takes for the heads to
> unload after parking. I have two of these disks sitting on my desk now
> collecting dust...
> /Morgan
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g"


The disks in question are indeed WD on one box, but they are all Caviar=20
Black and they performed well months ago with the very same hardware and =

an earlier FreeBSD 8 version.
The other boxes in questions do have a set of mixed type, Seagate, WD,=20
Samsung (mostly Samsung F1 types). We do not use 'Green' drives, due to=20
every box acts as a server and we found green-disks, even from WD, too sl=
ow.

Oliver




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