[mythtv-users] Another TFW, Error: Write() -- IOBOUND
covert covert
thecovert at gmail.com
Thu Aug 28 02:08:04 UTC 2008
On Tue, Aug 26, 2008 at 11:08 PM, George Mari
<george_mythusers at mari1938.org> wrote:
> George Mari wrote:
>> covert covert wrote:
>>> I am getting the dreaded "TFW, Error: Write() -- IOBOUND" error
>>> showing in my Mythbackend log. I hope someone can tell me what to
>>> check next. Done a few test and here are the results..
>>>
>>> While recording 1 x HD stream and 2 x SD streams.
>>>
>>> Output from iostat -xk 2 from just before I got a IOBOUND error to just after.
>>>
>>> -------
>>> Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s
>>> avgrq-sz avgqu-sz await svctm %util
>>> sda 0.00 754.00 16.50 15.00 66.00 3076.00
>>> 199.49 0.14 4.38 4.00 12.60
>>> hdb 0.00 0.00 0.00 0.00 0.00 0.00
>>> 0.00 0.00 0.00 0.00 0.00
>>>
>>> avg-cpu: %user %nice %system %iowait %steal %idle
>>> 28.33 15.98 5.08 26.39 0.00 24.21
>>>
>>> Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s
>>> avgrq-sz avgqu-sz await svctm %util
>>> sda 0.00 293.00 144.50 25.00 578.00 1272.00
>>> 21.83 1.29 7.59 5.71 96.80
>>> hdb 0.00 0.00 0.00 0.00 0.00 0.00
>>> 0.00 0.00 0.00 0.00 0.00
>>>
>> [deleted]
>>
>> That line just above - where the %util is 96.80 - tells you everything
>> you need to know. It means your single drive has reached the saturation
>> point in terms of IO operations per second. This is not the same as
>> bandwidth, forget about that. In a nutshell, it means the drive heads
>> are already bouncing around as fast as they possibly can, and they're
>> being asked to do still more.
>>
>> Separate your recording drive from your OS drive, at least. If you've
>> already done that, add another drive and use recording groups or RAID to
>> distribute the IO load among multiple drives.
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>
> Sorry - I meant storage groups, not recording groups...
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40 hours and no more IOBOUND errors in the logs. I enabled slow delete
in the backend options. Will keep an eye on it but it seems to have
fixed it.
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