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[Aaron Whitehouse <question106466@xxxxxxxxxxxxxxxxxxxxx>]

Question #106466 on Mythbuntu changed:
https://answers.launchpad.net/mythbuntu/+question/106466

Description changed to:
Hello all,

I've spent a long time trying to narrow this down, but I'm really
struggling and could do with any help/suggestions that you can come up
with.

I use an AMD 780G board with a 1TB Western Digital Green Power EAS HDD
and a 2.4GHz (or thereabouts) Sempron (Sparta) LE-1200CPU. I have 2 GB
RAM and have just added an nVidia 8600GT 512MB. I was previously using
analogue TV over a pvr150 tuner and a bttv tuner. I have just replaced
the pvr150 and bttv with a Hauppauge hvr-2200.

I have run Mythbuntu for quite a long time. We used 9.10 without too
much trouble. At some point near the beginning of this year (I don't
know what triggered it), Mythbuntu started stalling for 1-3 minutes at a
time, with the hard disk light on solidly and nothing else working. The
system would be virtually unresponsive, but would slowly crawl to a
terminal etc. Then, after about 1-3 mins, it would be back to normal. I
can't see anything that could be causing the problem in top, iotop or
the system logs. It is very difficult as the issue causes a whole bunch
of other issues in the logs (such as buffers filling up or kernel events
timing out), making it hard to pick the symptoms from the cause. On a
practical note, stalls during a recording often stop the recording
taking place, which is pretty unhelpful for a PVR. In top there is often
a very high percentage of "wa", which I understand means that a lot of
things are waiting for I/O.

I have now changed the card to an nVidia and am using the proprietary
drivers. I've replaced the tuner cards. I upgraded the system to Lucid
Beta and downloaded all the latest updates. The problem is still
occurring, even when all I was doing was browsing folders in Thunar.  To
give an idea of the problem, running a 42 minute video in VLC took 53
mins with the stalls.  The memory looks okay (I have 2GB in it), with
free -m showing most "used", but "cached".

On a few occasions when it has stalled, I have killed mythbackend (sudo
stop mythtv-backend) and the system continues stalling for another
couple of minutes. I had decided that the problem could be the hard
drive itself, because I would get a lot of stalls whenever it was
accessing the drive (such as when browsing in Firefox or copying files)
so I tried to copy all of the files from the disk to an eSATA disk. I
had also heard some rumours about issues with Green Power drives.
Mythbuntu/Thunar said that this would take 42 hours for 200GB over eSATA
(and seemed to be taking about that long for the first couple of hours
or so — it initially said 7ish hours, then I set the ionice to BE7 so
that it could do a recording, but it went up to 42 and didn't speed up
after the recording finished), but rebooting to a live CD of Ubuntu
Lucid Beta 2 did the job in 2 hours. This suggests to me that it isn't
the disk, but that talking to the disk in Mythbuntu has issues that
aren't in Ubuntu. I saw stalls in Mythbuntu before I configured it or
imported my database, which makes me think that it is unlikely a corrupt
database or similar. I'm struggling to think of anything that is
different between Mythbuntu and Ubuntu that I haven't tested and
eliminated as a cause.

Given that it isn't showing in top/iotop, I'm wondering if it is
something really low-level. On the other hand, I would have thought it
would need to be hardware/Mythbuntu-specific or everyone would be
complaining. I've replaced most of the hardware that I thought could be
causing the issues.

If anyone can help me, it would make a huge difference -- even if only
to suggest more diagnostics or logs to review.

Thanks in advance,

Aaron

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