[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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