[mythtv-users] zfs-fuse anyone?

[David Wilhelm]

On Thu, Dec 9, 2010 at 10:19 AM, Richard Shaw <hobbes1069 at gmail.com> wrote:
>> On Thu, Dec 9, 2010 at 6:42 AM, Stefan G. Weichinger <lists at xunil.at> wrote:
>>>
>>> Does anyone of you run zfs-fuse (on linux. Not ZFS on solaris or so) for
>>> mythtv-storage?
>>>
>>> I consider doing so soon ... and would like to hear any experience if
>>> available.
>>>
>>> Thanks, Stefan
>>
>> I know ZFS has some (at lot of) advantages for the system
>> administrator, but this recent review[1] shows quite a bit of
>> performance penalty.
>>
>> Richard
>>
>> [1] http://www.phoronix.com/scan.php?page=article&item=zfs_fuse_performance&num=1
>
>BTW, This is actually a big improvement earlier zfs-fuse releases were
>much slower.
>
>John

I use zfs on my Myth back end (under Ubuntu 10.4) and have over a year
now.  I love it; it almost works too well for error recovery.  I had
bought 8 somewhat questionable drives, and when one failed I didn't
know for over a week because I didn't check any logs.  The system
continued to play HD content to two machines just fine with one disk
down, and when the replacement finally shipped, continued to play just
fine for the 12 hours it took to re-silver the disk.  From a "painless
fault tolerance" perspective, it doesn't get much better.  I've also
done a few system wipes and re-installs of  Ubuntu with this setup,
and never had a problem getting the zpool back online.

There are some caveats though:
1) I have a separate disk for the system installation; it isn't on the
zpool (and I don't think it can be under fuse)
2) It eats about 20% (spiking as high as 40%) of one CPU core (2.7 ghz
Athlon X2) when under fairly heavy load.  Might be an issue for a
single core atom back end, but otherwise it's not bad.
3) Performance could be an issue if this machine has other uses
besides myth (specifically anything working with lots of small files.)
Performance isn't bad at all (though not great) with large files such
as video files.  This is especially true of reads, as the link John
posted shows.  I only get around 80MB/s writes to the disk array on a
bad day, but even the blue-ray spec is around 1/10th of that.
4) Right now I'm not using myth as a DVR, only to manage my media
collection, so I can't comment for sure on video capture.  I do
however also use the machine for development and video work, and there
hasn't been any stutter or other issues when compiling, transcoding,
etc. while the machine is in use as both a back and front end.

~Dave