[mythtv-users] Odd i/o issues

[Michael D. O'Brien]

On Tue, Jan 13, 2009 at 3:13 PM, Michael D. O'Brien <obrienmd at gmail.com>wrote:
>
>> In the last week I've upgraded my back and frontends to Ubuntu 8.10 and
>> the newest myth-fixes.  Last night, I noticed that the show I was viewing
>> was pausing every few seconds, rendering it nearly unwatchable.  I knew the
>> backend was recording a few other shows and the frontends hadn't shown this
>> behavior while the backend was idle earlier that day, so I did some looking
>> around:
>>
>> -top on the backend and frontend showed plently of available memory and
>> idle cpu
>> -it's not a network issue, the maximum usage in iftop on the frontend
>> looked to be about 12mbps (out of 100) and on the backend around 30mbps (out
>> of 1000), due to recording 2 shows off our hdhomerun while I was watching
>> this other show.
>> -on the backend, top shows iowait hovering around 20-40%, which isn't bad
>> and was common while recording 3 HD shows and watching 1
>> -on the backend, iostat -xk 1 shows something interesting: my raid5 array
>> participants are all being used, but it seems that two of the drives hover
>> around 10% usage, while one is constantly pegged at 100% usage.  Is this
>> normal behavior in iostat -xk for a raid5 array?  it seems odd to me.
>>
>> My backend is a C2D e6320 with 3GB of ram running Ubuntu 8.10 and the
>> newest myth-fixes.  Myth records to a raid5 array of 3x750gb drives with a
>> 1.5tb xfs file system on top.  It's connected to the network via 1000bT
>> ethernet.
>>
>> My frontends are AMD x2 4000+ with 1GB of ram running Ubuntu 8.10 and the
>> newest myth-fixes.  They are connected to the network via 100bTX ethernet.
>>
>> Thoughts?  I'm intrigued by the what seems to be strange iostat results on
>> the backend...
>
>
> smartd?
>

SMART values look fine for all drives.  Also checked xfs file system, it's
clean and not fragged at all.
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