[mythtv-users] disk full, can't delete files

Chris Adams rocket at extremelan.net
Wed Nov 11 07:47:19 UTC 2009

On Wed, Nov 11, 2009 at 1:57 PM, Michael T. Dean
<mtdean at thirdcontact.com> wrote:
> On 11/10/2009 07:43 PM, Chris Adams wrote:
>> What is the minimum free space set to out of the box? Can I suggest it
>> be defaulted to something sensible (for our modern world of terabyte
>> hard drives), perhaps 1-2GB?
>> I have no idea where this would be set but if someone can point me in
>> the right direction I'll be happy to supply a patch..
> It's set to 1GiB by default, but depending on configuration, this may not be
> enough extra space to allow Myth to react in time when the system has
> multiple and/or high-bitrate recorders.
> And, even for a single, low-bitrate recorder, if the filesystem has its own
> limit on it (the reserved space allocated by most file systems), the "Extra
> Disk Space" setting needs to be set to a value greater than the amount of
> reserved space.  For example, ext2 and ext3 (and likely ext4) allocate 5% of
> the file system as reserved blocks only usable by root.  1GiB is 5% of
> 20GiB, so on a larger file system, it may be "full" long before you hit that
> 1GiB point.  Since most hard drives are very large, increasing this value to
> sufficient size to handle reserved space that /should/ be enabled on all
> root file systems would make the initial value huge--if you assume the
> average hard drive used to contain a root file system is only 160GB, we're
> talking 8GB, for 320GB it's 16GB, and so on.
> However, I don't think increasing the default is a good idea.  For those who
> do have dedicated file systems for MythTV recordings, they're often created
> (or tuned) to have 0 reserved space.  And, since the "Extra Disk Space"
> setting in MythTV applies equally to all file systems used by MythTV, we're
> actually reserving "Extra Disk Space" x number of file systems, so it adds
> up fast when larger values are used (16GiB with 5 file systems is
> 80GiB--enough for >10hrs of ATSC HDTV or 40 or more hours of SDTV).  The
> value it currently uses is reasonable for a dedicated partition--which is
> what most people use (possibly after having issues with using the root
> partition :).
> Mike

"One partition for everything" is the default for Mythbuntu.
Partitioning is hidden away in linux installers (and Ubuntu Wubi lets
you install to a file in your windows partition), which leads me to
believe partitioning is just too damn complex for most users to grasp.
In other words David's problem is going to happen fairly often..

Not knowing ANY of the myth code, I'm going to guess this recording
was started with the system at say, 1.2GiB of free space and recorded
happily until the disk ran out. Meanwhile whatever part of myth that
monitors free space didn't get run often enough to see that the space
dropped below 1GiB and autoexpire something. Does that sound anything
like the way myth works?

A note about the effect of the setting on multiple partitions as
well.. for users with complex setups (yes 5 partitions for myth
recordings is pretty complex!) those users can and will discover the
setting, and they'll tweak it as they like.

Does anyone know where in myth the code lives that handles this?

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