[mythtv-users] IOBOUND: Arrrg, will it ever end?

Donavan Stanley geckofiend at gmail.com
Tue May 17 13:14:56 UTC 2005

On 5/17/05, Donn <sharky at gmail.com> wrote:
> A. Changing from ext3 to xfs. Better performance? Not really sure disk
> i/o is the problem, except maybe when the two recordings first start
> up?  Disk i/o doesn't seem to be that much when recording two shows
> simulataneously and when the iobound msgs are absent.  Using vmstat:
> bo ~4000-8000 with lots of bo=0 every other second.

If you're IOBOUND then IO is the problem.  Ext3 is a horrible choice
for a media machine, so even if that doesn't solve your problem it's
worth switching to xfs/reiser.

> B. Going back to a frontend & backend in ONE pc: 3.4GHz P4. I didn't
> have these blasted iobound problems before splitting the FE and BE.
> Kinda weird.

Or replacing the machine you're using as a backend if you want to get drastic.

> C. Change my LVM volumegroup to a single drive because one drive is
> reported as UDMA(33) but the other drive is seen as UDMA(100).

I've never mixed and matched them in an LVM like that.

> This seems to be a backend-only problem. Happens when the frontend is
> idle. Though, I have suspected that playback i/o exasperates the
> problem. No proof though.

It would make sense.  If your disk is having trouble keeping up when
writing then it's going to get worse when reading from it as well,
especially when dealing with HD streams.

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