I have a script that rotates hourly, daily and monthly snapshots. Each
filesystem has about 40 snapshots (zfsList.png - output of 'zfs list | grep
-v home/' -  the home directories datasets are snipped from the output. 4
users in total.)

I noticed that the hourly snapshots on the heaviest filesystem in use are
about 1.2GB in size where on the other system the regular NFS exported
filesystem has about 60MB snapshots (gallerySnapshots.png - output of
command 'zfs list -t snapshot -r pool01/utils/gallery')

I know that the gallery FS is in heavier use then normal but I was told it
will be mostly reading and based on the iostat seems that there is heavy
writing too.

I guess I'll schedule some downtime and disable gallery export and see if
that will effect the number of write operations and performance in general.

Unless there is some other way to test what/where these write operations
are applied.

The 'zpool iostat -v' output is uncomfortably static. The values of
read/write operations and bandwidth are the same for hours and even days.
I'd expect at least some variations between morning and night. The load on
the servers is different for sure. Any input?


-- Peter

On Wed, Jan 16, 2013 at 7:49 PM, Bob Friesenhahn <
bfrie...@simple.dallas.tx.us> wrote:

> On Wed, 16 Jan 2013, Peter Wood wrote:
>> Running zpool iostat -v (attachment zpool-IOStat.png) shows 1,22K write
>> operations on the drives and 661 on the
>> ZIL. Compare to the other server (who is in way heavier use then this
>> one) these numbers are extremely high.
>> Any idea how to debug any further?
> Do some filesystems contain many snapshots?  Do some filesystems use small
> zfs block sizes.  Have the servers been used the same?
> Bob
> --
> Bob Friesenhahn
> bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/**
> users/bfriesen/ <http://www.simplesystems.org/users/bfriesen/>
> GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
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