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Re: sizing log - is there a too big?

To: aurfalien <aurfalien@xxxxxxxxx>
Subject: Re: sizing log - is there a too big?
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Thu, 27 Jun 2013 11:48:10 +1000
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <55C24454-59E9-4285-9A4C-C4BD24EDBEEC@xxxxxxxxx>
References: <55C24454-59E9-4285-9A4C-C4BD24EDBEEC@xxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
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.

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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