[mythtv-users] USB 2.0 Drive Performance Issues

Nick Morrott knowledgejunkie at gmail.com
Tue Apr 15 17:29:52 UTC 2008


On 15/04/2008, Drew Tomlinson <drew at mykitchentable.net> wrote:
> On 4/15/2008 3:45 AM Nick Morrott said the following:
>
> > On 15/04/2008, Drew Tomlinson <drew at mykitchentable.net> wrote:
>  >
>  >
>  >>  I'm surprised this would affect playback as now recordings are on a
>  >>  separate drive.  Maybe USB 2.0 requires more CPU than ATA drives with
>  >>  DMA enabled?  Can anyone explain this behavior?  I'm just curious as I
>  >>  still intend to install my other drives and move the external to SATA.
>  >>
>  >
>  > USB devices can use high levels of CPU during transfers. A DMA-enabled
>  > ATA disk should only use minimal CPU. Also don't forget that whenever
>  > you are playing back video or using MythWeb, the MySQL database is
>  > being read at the same time. If performance still suffers when you
>  > have your eSATA disk online (I'd guess it will be better than USB) and
>  > it's due to disk I/O rather than CPU, you could move your database to
>  > another spindle.
>  >
>
>
> Thanks for your reply.  Just to be clear, the OS, MySQL database, and
>  everything except recordings are on an ATA-133 drive.  It's only the
>  recordings that are on the USB.  Thus I am still confused as to why
>  recording playback would have pauses and skips when using mythweb unless
>  it's just CPU contention.  mythweb should not be accessing the
>  recordings drive, correct?

MythWeb generates thumbnails from your new recordings for display on
the Recorded Programmes page, whilst playback of recordings and
MythWeb both access the database.

Run 'top' whilst you are seeing the playback pauses and skips - it
might give you an indication of where the bottleneck (CPU or I/O) is
occuring.

-- 
Nick Morrott

MythTV Official wiki:
http://mythtv.org/wiki/
MythTV users list archive:
http://www.gossamer-threads.com/lists/mythtv/users

"An investment in knowledge always pays the best interest." - Benjamin Franklin


More information about the mythtv-users mailing list