BackupPC-users

Re: [BackupPC-users] BackupPC_Link takes ages

2012-07-05 10:12:14
Subject: Re: [BackupPC-users] BackupPC_Link takes ages
From: Adam Goryachev <mailinglists AT websitemanagers.com DOT au>
To: backuppc-users AT lists.sourceforge DOT net
Date: Fri, 06 Jul 2012 00:10:12 +1000
On 05/07/12 23:53, jonas wrote:
> Hello again,
> 
> first, I forgot to mention an important detail: we changed from
> ext3 to xfs on the 5TB RAID10 array which holds all BackupPC data
> during the re-setup.
> 
> Am 05.07.2012 15:04, schrieb Adam Goryachev: no, this doesn't seem
> to be the problem. I didn't find any unexpected logs. The pc/$HOST
> directory shrinks a lot during the link-process, so I consider this
> as evidence that pooling actually works as expected. I did
> recognize though, that the pool directory is empty on all BackupPC 
> servers. All pooled files seem to be stored in cpool instead. Is
> this expected?
compressed files are in cpool, so this suggests you have compression
enabled (for file storage, not in transit). This is 'normal'.
> 2) Filesystem or hard drive layout/configuration (ie, RAID level, 
> layout, chunk size, ext3 compared to jfs, etc) As written above:
> moved from ext3 to xfs as we thought that this might increase
> performance.
Obviously this is the big change, so you should probably start here. I
would suggest reading up on how to optimize xfs for backuppc, or
generically, a large number of small read/writes.

I recently subscribed to the linux-raid mailing list for a backuppc
related issue in fact, and saw a few un-related (to me) posts regarding
default raid stripe size, and (I think it was) xfs file system being
problematic. I think there is some relationship with the FS storing some
type of data every x bytes per disk, and if this data all ends up on the
same physical disk (or in your case pair of disks) then you end up with
a dis-proportionate amount of load on a small subset of your disk array.
It seems you are using hardware raid which presents the disk as "sdk",
however, the basic idea would still apply (stripe size of the raid and
block size of the FS).

I'd suggest to subscribe to the xfs mailing list, and/or look into how
you should optimise your filesystem to improve performance (defaults are
not always ideal).

Regards,
Adam

-- 
Adam Goryachev
Website Managers
Ph: +61 2 8304 0000                            adam AT websitemanagers.com DOT 
au
Fax: +61 2 8304 0001                            www.websitemanagers.com.au

-- 
Adam Goryachev
Website Managers
www.websitemanagers.com.au


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