help needed - tuning a filesystem for rm and cp ? (more details)
Eric Anderson
anderson at freebsd.org
Tue Aug 14 20:24:03 PDT 2007
On 08/14/07 16:47, Gore Jarold wrote:
>>> Here is a question for any and all out there
> reading
>>> ... what would you expect would happen to a system
>>> that was constantly maxing out this value,
> sometimes
>>> on a sustained basis, while the activity that
> caused
>>> it went on uninterrupted ?
>>>
>>> I am seeing the system halt ... is it reasonable
> to
>>> think that maxing that value out on a regular,
>>> sustained basis would cause a system to halt ?
>>>
>>> (6.2-release running on a 4 GB memory p4 xeon ...
> does
>>> nothing but fileserver duties)
>>
>> If you have a lot of meta-data IO (which you seem to
> have), then it's
>> possible that the system is incredibly busy doing
> disk accesses, and
>> waiting on IO from storage. When you say 'halt'
> does that mean you
>> can't log in to it, and eventually it comes back
> alive, or does that
>> mean it is locked up in a way that never recovers?
>
>
> I never wait around to find out it it comes back ...
>
> It no longer responds to pings, so I assume it is
> actually crashed.
>
> Also, it should be noted that this system (and its
> large, >4TB filesystem) has quotas enabled.
>
> So perhaps a better question would be:
>
> Any comments on frequent, sustained maxing out of
> dirhash on a quota'd filesystem ?
If you can, it would be best if you can break into the debugger and get
a core.
I can't think of how dirhash would effect quotas really, but I suppose
it might be possible. You might try bumping the dirhash setting way up,
maybe to 20MB or so. I think it might be worthwhile also to run a
script (cron maybe) every minute that logs the current use of dirhash,
and maybe a ps -auxwl, with a date stamp so you can when your peaks
occur, what was running, etc, just before a crash.
Might also look into bsdsar - it might help with some of this too.
Eric
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