[mythtv-users] strange order of expiry

Brian J. Murrell brian at interlinx.bc.ca
Fri Oct 20 11:44:21 UTC 2017

On Thu, 2017-10-19 at 23:00 -0400, Michael T. Dean wrote:
> On 10/19/2017 04:54 PM, Mike Holden wrote:
> > 
> > Are all the files in the same Storage Group?

Yes.  But your question made me look deeper into this.  The storage
group that they are in is made up of multiple disks and indeed, the
disk that the expired/deleted recordings are happening in is the only
one low in space.

> I think, here, you mean multiple file systems (as opposed to Storage 
> Groups),

Indeed.  That is what he must have meant.

> but the Autoexpire List doesn't take into account file system 
> space (since the files could exist on any of many file systems and
> may 
> be moved at any time)--instead it's the "preferred" order of deletion
> of 
> recording files.

Right.  But the autoexpire list is what is used when space needs to be
freed in a filesystem for a new recording.  That is the activity that I
was observing that was making me wonder why things were being deleted
out of order in respect to the Autoexpire List.

> When an actual recording begins and MythTV determines 
> that space is required on the file system to which it's recording,
> it 
> goes through the recordings on the Autoexpire list until it finds
> the 
> first (most-preferred) one that exists on the file system in
> question.

Right.  Which leads to what looks like out-of-order processing.

> I just got a chance to actually look at the code, and the reason
> MythTV 
> is preferring deletion in an order different from that specified by
> the 
> autoexpire settings is due to the fact that these recordings aren't 
> truly "autoexpiring"--in that they're not recordings MythTV is
> removing 
> from the system without user request. Instead, because they're all 
> Deleted recordings, they're just recordings that the user has
> already 
> deleted whose space isn't yet needed, so they're being kept until
> the 
> space is required.  In the case of Deleted recordings, they're
> removed 
> in first-in-first-out order (in other words, in the order in which
> they 
> were deleted by the user).

So this still seems unintuitive.  The Deleted recording group seems to
me to be a pool of recordings from which space can be recovered.  It
still seems that the autoexpiry ordering ought to apply there on the
assumption that if a user wants to recover a recording from it, they
are most likely going to want to recover something of higher priority. 
Maybe.  :-)

In any case, the source of my actual confusion has been cleared up.

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