[mythtv-users] MythTV recording extra time *randomly*

Yeechang Lee ylee at pobox.com
Mon Feb 23 21:49:26 UTC 2009

Misty P <mistyp at thekorn.net> says:
> Occasionally MythTV will decide to add extra time onto my recordings, 
> seemingly at random.

In addition to Mike Dean's suggestions, two other (less likely)

* Check Settings|TV Settings|General. Is anything listed under
  "Category record over-time"?

  In my case, Sports event is entered there with a 30-minutes setting,
  so all sports recordings get an extra buffer at the end--independent
  of any soft or hard padding settings in the recording rule--for
  overtime and such. (As I don't record sports very often I don't know
  offhand if the scheduler treats this as hard or soft padding.)

* I have seen recordings get randomly "extended" if the disk
  mythbackend is writing to is unusually busy.

  On my 16-drives RAID 6 array, if I edited smartd.conf to run the
  long and short self-tests, this will cause one or more of the drives
  (all Western Digital RE2) to hang (utilization shoots to near 100%
  in 'iostat -xk 2') for long periods. So I disabled the long tests
  but kept the short ones. I found, unfortunately, that even the short
  tests would sometimes randomly cause one of the drives to hang in
  the same way, typically at the 10% level of the self-test as visible
  via 'smartctl -a /dev/sdx'. So I had to disable the short tests,
  too. Anyways, during these hangs, recordings that write to the array
  will see random elongations of recording times, I guess because
  mythbackend is determined to record a 30-minutes sitcom for 30 clock
  minutes even if for 17 out of every 60 seconds the array isn't
  writeable to.

  I presume that if you were running smartd with self-tests set up
  you'd know, but my point is that any situation in which the
  recording array gets super-busy (not just a Web browser being
  brought up in the background, or something) has the potential to do
  this, at least on my -fixes setup.

Frontend/backend:	P4 3.0GHz, 1.5TB software RAID 5 array
Backend:		Quad-core Xeon 1.6GHz, 6.6TB sw RAID 6
Video inputs:		Four high-definition over FireWire/OTA
Accessories:		47" 1080p LCD, 5.1 digital, and MX-600

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