[mythtv-users] Disk Space Problem

Peter Bennett (cats22) cats22 at comcast.net
Sat Oct 27 13:39:50 UTC 2012


I noticed recently that some of my recordings are cut short. Upon
looking at the logs I found some 6 recordings ran out of disk space with
messages like this.

Oct 24 21:11:44 panther-ux mythbackend[2659]: E TFWWrite
ThreadedFileWriter.cpp:529 (DiskLoop)
TFW(/srv/mythtv/video3/recordings/1041_20121024210000.mpg:70): No space
left on the device for file
'/srv/mythtv/video3/recordings/1041_20121024210000.mpg'#012#011#011#011file
will be truncated, no further writing will be done.

All of the file systems are 99% full, but about 30% of the recordings
are deleted, so can be expired. I had thought that mythtv would
automatically take care of expiring enough space for new recordings.
There is nothing on these file systems other than mythtv recordings, so
it is not caused by some other process filling up space.

This happens when 3 HD recordings take place at one time and they are
all on the same file system. At that rate it would use about 1 GB every
3 minutes.

I am updating the free space specification in the front end from 1 GB to
5 GB. What is the recommended value?

What is the recommended approach for free space?

I also wonder how it is deciding which file system to use. The "Balanced
Free Space" scheduler is selected, and according to the documentation
that will allocate recordings on the disk with most free space. Since
all disks are 99% full, the one with the most free space will randomly
depend on the size of the last program expired and what was recorded
since it was expired. I have three files systems of very different sizes
and I expect it to make more use of the largest file system. I don't
think this algorithm will achieve that. It may even select a smaller
file system with nothing expirable on it, and then be unable to complete
the recording, instead of using another file system which may have many
expirable recordings available.

Perhaps I should change the expire setting to expire programs a few days
after deleted, so that a realistic free space will be seen? Or have I
misunderstood how the balanced disk scheduler works?

Peter



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