[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.
>> _______________________________________________
>> mythtv-users mailing list
>> mythtv-users at mythtv.org
>> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>>
>
> Sorry - I meant storage groups, not recording groups...
> _______________________________________________
> mythtv-users mailing list
> mythtv-users at mythtv.org
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>

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.


More information about the mythtv-users mailing list