[mythtv-users] Unstable Backend - Full Media Drives but Plenty to Autoexpire

[Nick Rout]

On Mon, Nov 8, 2010 at 6:00 PM, tortise <tortise at paradise.net.nz> wrote:
> On 8/11/2010 11:54 a.m., Michael T. Dean wrote:
>>
>> On 11/07/2010 02:30 PM, tortise wrote:
>>>
>>> My mythbuntu 10.04 64 bit backend with a ~100G OS HDD and 2 media 2TB
>>> drives I've noticed to start missing recordings, duplicate recordings
>>> and have a few crashes. I've installed apport and managed to submit
>>> one so far, that seemed to be to do with time issues. I upgraded from
>>> 23.0 to 32.1 thinking that might help.
>>>
>>> I realise now what is also different is the media drives are now full,
>>> but they have 500G of Space Available After Auto-expire. I am
>>> wondering if the problems arise from my expecting mythtv to just do
>>> the deletions without issue. Anyone else experienced similar, or can
>>> someone confirm that we need to do the auto deletions ourselves?
>>
>> MythTV only ever expires shows /after/ starting to record--and /only/
>> from the file system to which it's recording. It also chooses where to
>> record without looking at auto-expire space (based on your selected
>> Storage Group Disk Scheduler:
>> http://www.mythtv.org/wiki/Storage_Groups#Storage_Group_Disk_Scheduler
>> ). Therefore, if MythTV is recording to a file system which has no
>> expirable recordings, it will fill the drive, and Bad Things Happen.
>>
>> Also, if your file system is in bad shape--i.e. something you might
>> expect from a certain file system once it's more than 80-some-percent
>> full--it can cause problems that could conceivably slow deletion to the
>> point that the drive fills up before space is made available.
>>
>> Also, if your system is unable to expire recordings--due to file system
>> permissions or getting "stuck" on a particular recording (this happened
>> for a while, at least with 0-byte recordings)--then it won't be able to
>> make space to record more.
>>
>> Mike
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>>
>
> All 3 filesystems in my case are ext4, I think they are now the default
> mythbuntu install filesystems (10.04 and possibly 9.10 as I recall), I saw
> no reason to change that (quite the contrary!)
>
> I also note that the first media 2TB drive has 0 bytes left on it, which
> surprised me, as I expected an expected show > space available to be
> recorded on the other drive, 0 bytes suggests otherwise to me.
> So I had a look and see that 3 mpg's all finish at the same time, presumably
> when the drive got full, 9:53:34 yesterday.  I am guessing that is one time
> the BE got its wires crossed...and needed a reboot.
>
> I also note, from the above URL reference, that my Storage Group Policy
> (under backend General setup) is "Combination" which I assume was the
> default when I setup (and that the default changed post 10.04?) as I do not
> recall a reason to change it, however I've now changed it to "Balanced Free
> Space" so can see how that goes.  I guess the issue here is the simultaneous
> recording capacity of one disc's pipe in.  Again at a guess if I can record
> 5-6 HD shows simultaneously to one HDD then I'm very unlikely to have a
> problem.
>
> Also suggests to me that if choosing two HDD's for media, that its
> preferable to add clean ones together, so the recordings get shared out more
> or less equeally, however I expect most people do it as I have, add another
> disc when its needed....

you can of course do some manual balancing with the mv command. One of
the points about storage groups is that it doesn't matter to the
system which drive within the SG a file is on.