[mythtv-users] Another TFW, Error: Write() -- IOBOUND
George Mari
george_mythusers at mari1938.org
Tue Aug 26 13:08:56 UTC 2008
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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