background fsck high load on 8.1

[Sergi Seira]

Hello,

Yes, we are considering ZFS, or waiting for journaled soft updates on 9.X.
This issue only happens on unexpected reboots, which aren't that frequent.

Mr. McKusick response to my question on freebsd-fs mailing-list was :
"...
This is the first report that I have heard of the higher level of
slowdown by background fsck on 8.X systems. My guess is that it
comes about from work done to make the I/O subsystem faster which
in turn allows fsck to have a higher impact.

For a period we were working on a kernel feature (associated with
nice) that would allow the system to throttle I/O activity for a
given process. It turns out to be a much harder problem than it at
first appears. We set this aside when we got journaled soft updates
working as they eliminate the need for background fsck. While
journaled soft updates are too big of a change to be merged back
into the 8.X tree, we do expect them to be used by default on 9.X
systems.
..."

Thanks for your help,
regards,
Sergi

On 12/04/11 17:51, Steven Hartland wrote:
> The cpu requirements are usually quite low for fsck, what your
> most likely seeing is disk contention due to the amount of IO.
>
> Personally I would recommend to consider moving to 8.2 + ZFS as
> our filing system as it removes fsck from the equation, as well
> as giving lots of other benefits.
>
> Regards
> Steve
> ----- Original Message ----- From: "Sergi Seira" <s.seira at cdmon.com>
> To: <freebsd-stable at freebsd.org>
> Sent: Tuesday, April 12, 2011 2:23 PM
> Subject: background fsck high load on 8.1
>
>
>> Hello,
>>
>> we've experienced that background fsck on 8.1 degrades server
>> performance on a higher degree than in previous fbsd versions (6.3,
>> 7.3; amd64).
>>
>> We've noticed it after upgrading - same hardware - to a 8.1-RELEASE.
>> Now, performance of other services (i.e. apache, mysql) during a
>> background fsck falls miserably.
>>
>> Is there any way to calm fsck down?, nice(1)?, some sysctl?
>>
>> We have also gmirror, but we prevent to rebuild it if there is a fsck
>> running in background.
>
>
> ================================================
> This e.mail is private and confidential between Multiplay (UK) Ltd. and
> the person or entity to whom it is addressed. In the event of
> misdirection, the recipient is prohibited from using, copying, printing
> or otherwise disseminating it or any information contained in it.
> In the event of misdirection, illegible or incomplete transmission
> please telephone +44 845 868 1337
> or return the E.mail to postmaster at multiplay.co.uk.
>
> _______________________________________________
> freebsd-stable at freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-stable
> To unsubscribe, send any mail to "freebsd-stable-unsubscribe at freebsd.org"