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

[tortise]

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....

Also makes me wonder which file systems need the slow deletes?  And more 
specifically does ext4 need it?