Re: Performance problems with 3ware 9500S-4LP and 2.6.25-rc3

Chris Snook
2008-02-27T19:57:27Z

Andre Noll wrote:
> On 13:33, Chris Snook wrote:
>
>>> During the daily cron job that uses rsync to sync a 500G file system
>> >from another machine to the raid on the 3ware controller the load
>>> jumps up, and the machine becomes sluggish as hell. For example, an
>>> ssh login to that machine takes minutes to complete and ldap becomes
>>> unreliable while the rsync job is running. Even Nagios complains
>>> about the machine being down while rsync is running.
>> You're putting your box under astronomical load. This is generally
>> regarded as a bad idea, regardless of how well your storage controller
>> is performing.
>
> The machine becomes sluggish also when I write directly to the raid
> array. A simple
>
> dd if=/dev/zero of=tmpfile
>
> shouldn't push the load up to 4, right?

Actually, it's normal for pdflush to spawn up to 8 threads when you're
dirtying memory faster than it can be written to disk. Load going to 4
is not abnormal. ssh logins taking minutes is very abnormal.

>> Can you measure the single-threaded throughput (say,
>> coping one huge file, and then syncing) to give us a baseline
>> performance figure?
>
> Single threaded throughput seems to be ok (140M/s). The problem is
> that the machine becomes unresponsive.

Does the machine become unresponsive during the single-threaded test, or
only when doing the rsync?

-- Chris