[mythtv-users] Massive HDD activity at show starts

[Mark Kendall]

On 3 June 2010 17:17, Jan Schneider <jan at horde.org> wrote:
> Hi,
>
> I'm experiencing something in 23-fixes that didn't happen with 22-fixes and
> seems to be worse when wathing HD channels:
> if watching LiveTV, when one shows ends and the next one starts, there is so
> much (audible) HDD activity (i.e. probably seek operations), that a lot of
> frames are dropped (from current LiveTV as well as recordings that happen at
> the same time). Sometimes up to one or two seconds are missing. In the worst
> case the FE is so much off the track, that I have constant audio pauses
> until I restart LiveTV.
>
> This is a combined BE/FE with XFS for recordings and ext3 for anything else.
>
> I'm wondering:
> - What is causing this much activity? There should be just 2 or 3 DB INSERTs
> beside the regular recording activities, right?
> - Why is this happening now?
> - How can fix this, or at least track the cause further down?

3 possible causes come to mind:-

- Preview generation. I've been trying to track down some problems
with the frontend spawning multiple preview generation threads in
trunk - it could well be occurring in 0.23-fixes as well. When you
'switch' to the new show, preview generation may be initiated for the
show that's just finished.

- Expiry of old recordings. This is more likely to happen with actual
channel changes and channel surfing, but I often see the backend
cleaning up short live tv clips after a channel change and this can
cause hiccups in the frontend.

- Switching to the new 'live tv recording'. The live tv switch code
could do with some love and it isn't always very graceful.

The easiest way to start tracking it down is to generate some logs
from the frontend and backend with -v playback logging.

regards

Mark