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List:       zfs-discuss
Subject:    Re: [zfs-discuss] [zfs-code] Peak every 4-5 second
From:       Robert Milkowski <milek () task ! gda ! pl>
Date:       2008-07-30 9:26:36
Message-ID: 16974610.20080730102636 () task ! gda ! pl
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Hello Bob,

Wednesday, July 30, 2008, 3:07:05 AM, you wrote:

BF> On Wed, 30 Jul 2008, Robert Milkowski wrote:
>>
>> Both cases are basically the same.
>> Please notice I'm not talking about disabling ZIL, I'm talking about
>> disabling cache flushes in ZFS. ZFS will still wait for the array to
>> confirm that it did receive data (nvram).

BF> So it seems that in your opinion, the periodic "burp" in system call 
BF> completion time is due to ZFS's periodic cache flush.  That is 
BF> certainly quite possible.


Could be. Additionally he will end-up with up-to 35 IOs queued per
each LUN and if he doesn't effectively have a nvram cache there the
latency can dramaticly increase during these periods.


-- 
Best regards,
 Robert Milkowski                            mailto:milek@task.gda.pl
                                       http://milek.blogspot.com

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