[mythtv-users] Delete files slowly

[Michael T. Dean]

On 01/26/2010 12:31 AM, Michael T. Dean wrote:
> On 01/25/2010 08:32 PM, Greg Oliver wrote:
>   
>> I just noticed that while I have the setting to delete files slowly,
>> and recording, it records faster than it deletes.
>>
>> Is there logic in this setting, or can I assume that it will always
>> delete slower than 19mb/s (1 tuner)..  I guess ultimately I would hate
>> to have frame loss because it is clearing disk space too slowly, but I
>> am not familiar with the logic.  It may very well delete much faster
>> as the available space gets lower, etc..
>>     
> It turns out that we used to have a minimum truncate rate of 8MiB/sec
> and would use that value or 120% the max recording bitrate (combined max
> bitrate of all cards), whichever was higher.  Before 0.21 was released,
> we removed the minimum truncate rate, so now do 120% ATSC max bitrate *
> number of cards (basically 2.78MiB/sec/card (including "virtual" cards
> for multirec)).
>
> After some discussion on IRC, we may re-institute the minimum truncate
> rate.
>   

While it sounds like this may have been an ephemeral issue caused by
something else writing to the disk drive, I did bump up the truncate
speed as well as restore the minimum truncate rate in trunk [23435].

This means that if you have 1 or 2 capture cards defined in your system
(where number of cards includes "virtual" cards used for multirec), your
system will truncate at 8MiB/sec (or about 2min 8sec per GiB), and 3 or
more cards will truncate at even higher rates (proportional to the
number of cards).  Before the change, a system with only one capture
card would have truncated at a rate of about 7min 24sec per GiB.

So, this change should add a bit more overheard both for systems with
many cards and for systems with only one or two cards.  Therefore, it
should even handle cases where the commflagger or transcoder or frontend
or whatever is spewing out a ton of log messages from libav* complaining
about the video or whatever.

Granted, if you have other non-Myth processes writing to the same disk,
you can still out-write the truncates, so we still recommend having
recordings directories on separate file systems not used by other apps.

Anyway, thanks for the report, and please let me know if you see any
other issues.

Mike