ZFS performance degradation over time

[Jonathan Noack]

On Fri, January 8, 2010 11:31, Garrett Moore wrote:
> No, I haven't isolated the cause to only be uptime related. In my original
> email I mentioned that "as suggested by someone in the thread, it's
> probably
> not directly related to system uptime, but instead related to usage - the
> more usage, the worse the performance."
>
> I've been starting my system with different combinations of applications
> running to see what access patterns cause the most slowdown. So far, I
> don't
> have enough data to give anything concrete.
>
> This weekend I'll try some tests such as the one you describe, and see
> what
> happens. I have a strong suspicion that rTorrent is to blame, since I
> haven't seen major slowdowns in the last few days with rTorrent not
> running.
> rTorrent preallocates the space needed for the file download (and I'm
> downloading large 4GB+ files using it), and then writes to them in an
> unpredictable pattern, so maybe ZFS doesn't like being touched this way?

Probably unrelated, but this prefetch issue results in a slowdown:
http://lists.freebsd.org/pipermail/freebsd-fs/2009-December/007481.html

-Jonathan