[mythtv] problem with HDTV in Australia

[Daniel Kristjansson]

On Fri, 2005-07-29 at 10:58 +1000, Hamish Moffatt wrote:
> On Fri, Jul 29, 2005 at 10:07:37AM +1000, Berry, David wrote:
> > Disk speed not up to scratch??

> I think this should show up as system time in top, but I see 50% idle.
> I'm running LVM across two disks, no RAID. Should be fast enough as the
> data rates aren't really very high - no more than 20Mbit/second, because
> that's all that can come in off the air.
When you first posted I assumed you just had a bad signal. But if you
only have 50% idle when just recording, something is wrong. It should
be under 10% unless this is a really low end machine.

My first guess would be that you should make sure DMA is working. Then
make sure that there aren't a lot of errors coming out of some driver.
hdparm and dmesg are your friends here.

Here's my hdparm on my first drive for comparison. It is really write
performance that you care about, but the read timings are an OK proxy.

bash-2.05b# hdparm /dev/hda

/dev/hda:
 multcount    = 16 (on)
 IO_support   =  3 (32-bit w/sync)
 unmaskirq    =  1 (on)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 readonly     =  0 (off)
 readahead    = 256 (on)
 geometry     = 16383/255/63, sectors = 123385122816, start = 0

bash-2.05b# hdparm -tT /dev/hda

/dev/hda:
 Timing cached reads:   3376 MB in  2.00 seconds = 1688.26 MB/sec
 Timing buffered disk reads:  144 MB in  3.04 seconds =  47.44 MB/sec

--
Daniel