[mythtv-users] Storage groups: how to set minimum free space for a drive

[Michael T. Dean]

On 03/20/2008 09:58 PM, Mike Smith wrote:
> How can I set a minimum free space level for just one storage group?

It's not currently possible.  In truth, though, you need to be able to 
set a minimum free space level per /filesystem/, not per storage group.  
Multiple storage groups could use the same filesystem (so whose min free 
space would take precedence?) or a single storage group could use 
multiple filesystems (i.e. your root filesystem with 10GB available and 
your large recordings filesystem with 500GB available, so do you really 
want to keep 50GB free on both?).

> I found the option in the TV Settings area of the front end, but that 
> seems to be a global minimum,

It is.

> because I set it to 3 GB and my root drive just filled up again 
> (taking with it my recording of Lost, for which I'll catch hell from 
> SWMBO as soon as she realizes). There's plenty of space on my two 
> other directories in that group.

But not in the way you think.  The "global" setting "Extra Disk Space," 
specifies the amount of extra space to keep available on /each/ 
filesystem, not a total amount of extra space to keep available across 
all filesystems.  Therefore, if you set the "Extra Disk Space" to 3GB, 
it should be keeping 3GB available on all filesystems (to which Myth is 
recording at any particular time).

That parenthetical can actually be /very/ important.  If Myth is not 
recording to a filesystem, it does /not/ autoexpire programs to make 
room for the data that some other process is writing to that 
filesystem.  Therefore, until a recording starts /and/ is being written 
to the filesystem in question, no programs will be expired from that 
filesystem.

And, another very important thing (that I'm sure you've figured out, but 
I'll mention just to be perfectly clear) is that Myth will /only/ expire 
recordings to make space available--i.e. it won't delete data it doesn't 
own.

Note, also, that it's possible Myth may not identify a filesystem as 
being unique, but we'd need a lot more detailed information to prove 
this is what's occuring for you.  It's far more likely that something 
else (i.e. MySQL bin logs - http://mythtv.org/docs/mythtv-HOWTO-6.html ) 
is filling up your root partition when Myth isn't using it and causing 
your system to crash.

> Is there some way to prevent this from happening again, or do I have 
> some fundamental problem with my understanding of this new feature?

Just need to figure out what is filling up your partition.  As others in 
the thread have mentioned, autoexpire should be getting rid of 
recordings for you if they were filling up the partition, and the "Extra 
Disk Space" does what you probably initially thought it would, so it 
should be working for you.

You may also have realized that the current setting has the same problem 
that the "single-storage-group-using-multiple-filesystems" case 
described at the top does--it imposes a free space limit on all 
filesystems, regardless of filesystem size.  I may eventually make a 
patch to modify this (either to a global percentage free space available 
or a per-filesystem free space available), but doing so isn't currently 
high on my list (as I'm not currently using the setting to reserve extra 
free space).

Mike