[mythtv-users] Stuttering on some mpg files (PrebufferEnoughFrames)

[Stuart Morgan]

On Monday 23 Dec 2013 19:13:44 Stuart Morgan wrote:
> On Monday 23 Dec 2013 13:05:26 Ian Evans wrote:
> > > yep, it's the USB drive. Don't know why it's giving me speeds so slow:
> > > 
> > > sudo hdparm -tT /dev/sdc1
> > > 
> > > /dev/sdc1:
> > >  Timing cached reads:     2 MB in  2.05 seconds = 999.51 kB/sec
> > >  Timing buffered disk reads:   4 MB in  4.10 seconds = 999.83 kB/sec
> > 
> > rebooted and got this for the same drive:
> > 
> > Timing cached reads:   3578 MB in  2.00 seconds = 1789.24 MB/sec
> > 
> >  Timing buffered disk reads:  64 MB in  3.00 seconds =  21.30 MB/sec
> 
> Sounds like it's falling back to UDMA 0 (or worse) sometime after boot, the
> kernel falls back through different standards from fastest to slowest when
> it starts having trouble reading/writing to the drive at a higher speed.
> I've never seen a case where it falls back to reads at 1MB/sec though, that
> would suggest that either the driver is severely broken, or the drive is
> and the kernel is consistently finding that the drive is erroring out at
> higher speeds (UDMA 1-6, Sata 1-3).
> 
> This can happen particularly under heavy load. Once that happens it won't go
> back to full speed until a reboot. Keep an eye on syslog/dmesg and the
> appropriate sys node for that drive:
> cat /sys/class/ata_link/link1/sata_spd

Sorry, I just belatedly realised that you were talking about a USB drive so 
none of the above is relevant!
-- 
Stuart Morgan
MythTV