Re: sizing log - is there a too big?

aurfalien
2013-06-27T15:58:11Z

On Jun 26, 2013, at 6:48 PM, Dave Chinner wrote:

> On Wed, Jun 26, 2013 at 04:56:31PM -0700, aurfalien wrote:
>> Hi all,
>>
>> Wondering if my log being just under 2GB is a bad idea.
>>
>> Noticing flush-253:2/kcopyd which is my XFS file system getting
>> really high load avg and wait times via top).
>
> What has the log size got to do with something that is happening at
> the block layer? What's your storage config?
>
>> Doing a simple rsync over NFS and after a bit, the system gets to a load of 24.... yikes...
>
> Let me guess - 24 nfsds blocked waiting for kcopyd to do it's stuff?
>
> Load average going up when the NFS server is busy generally means
> your IO subsystem is heavily loaded - it's not uncommon to see large
> NFS servers that are extremely busy sustain load averages over a
> 100 (or even 1000) for hours/days on end....
>
>> Upon killing the rsync, I am seeing loads going down to sub 1
>> after about 10 min. I have repeated this to verify 10 min.
>
> Sure. Processes blocked on IO contribute to the load average. Kill
> the IO load, and the load average will return to nothing in 10-15
> minutes.

Not so fast my fine feathered friend.

Same work load, same hardware.

Only diff is;

External log, its 2GB
And its Centos 6.4 which was previously 5.9.
Its 16 drives in a hw raid 6, but 2 are for the mirrored journal and 1 for hot spare so 13 spindles. Before it was 14 spindles in raid 6 and 2 hot spare.

I did power cycle it late last night and will more closely observe today.

Very odd.

- aurf