[mythtv-users] Mythbackend recording glitches

Tue Oct 16 08:41:57 UTC 2018

On 16/10/18 06:18, Allen Edwards wrote:
> 
> 
> On Mon, Oct 15, 2018 at 9:05 PM Stephen Worthington 
> <stephen_agent at jsw.gen.nz <mailto:stephen_agent at jsw.gen.nz>> wrote:
> 
>     On Mon, 15 Oct 2018 19:26:10 -0700, you wrote:
> 
>      >> What sort of partition(s) are you recording to?  Please post the
>     fstab
>      >> line you are using for it, so we can see what options are being
>     used.
>      >> If it is on the same drive as the system partition, please post the
>      >> fstab line for that too.
>      >>
>      >>
>      >It is straight default Mythbuntu 16.041 on a single 750G drive. 
>     When I run
>      >out of ideas, I plan on buying a new 1T drive.
>      >
>      >dad at NewMyth:~$ more /etc/fstab
>      ># /etc/fstab: static file system information.
>      >#
>      ># Use 'blkid' to print the universally unique identifier for a
>      ># device; this may be used with UUID= as a more robust way to name
>     devices
>      ># that works even if disks are added and removed. See fstab(5).
>      >#
>      ># <file system> <mount point>   <type>  <options>       <dump>  <pass>
>      ># / was on /dev/sda1 during installation
>      >UUID=863a7857-d97e-432f-be2a-aa6d00f4e75d /               ext4
>      >errors=remount-ro 0       1
>      ># swap was on /dev/sda5 during installation
>      >UUID=e4227cca-c0b0-4da9-80ee-f6fd2d73abb9 none            swap    sw
>      >      0       0
>      >/dev/fd0        /media/floppy0  auto    rw,user,noauto,exec,utf8
>     0       0
>      >
>      >
>      >dad at NewMyth:/$ df
>      >Filesystem     1K-blocks      Used Available Use% Mounted on
>      >udev             1008340         0   1008340   0% /dev
>      >tmpfs             206196      6700    199496   4% /run
>      >/dev/sda1      718883112 269065760 413277092  40% /
>      >tmpfs            1030972     10196   1020776   1% /dev/shm
>      >tmpfs               5120         4      5116   1% /run/lock
>      >tmpfs            1030972         0   1030972   0% /sys/fs/cgroup
>      >tmpfs             206196         8    206188   1% /run/user/1000
> 
>     A simple ext4 partition with the default options should work fine, but
>     you might like to try it with barriers off to see if that makes a
>     difference - barriers affect the write performance of large writes
>     more than anything else.  Turning barriers off permanently is probably
>     not a good idea as it makes you much more vulnerable to having the
>     partition damaged in a power failure or similar situation.  If you try
>     with the "barriers=0" setting, as you are using the boot drive, you
>     may also need to add a similar setting to the kernel options in grub.
> 
>     Ext4 is OK for recordings, but XFS or JFS is considered better, as
>     they are more efficient at deleting huge files.  Ext3 is not
>     recommended unless you turn on the "slow delete" option, and even then
>     is not good.  I use JFS for all my recording partitions.
> 
>     The partition is nowhere near full - a full partition causes the heads
>     to move around a lot and that can cause problems.
> 
>     The best setup for MythTV is to have the system and database on an SSD
>     drive and the recordings going to their own (spinning rust) drive(s).
>     But I had my system working with recordings going to the same drive as
>     the system for a long time and it worked fine.  The disk was a
>     performance one though (Hitachi HDS723030ALA640 3 Tbyte 7200 rpm). And
>     I had the system on ext3 (and later ext4) and the recordings going to
>     a separate JFS partition on the same drive.
> 
>     I am wondering what version of MythTV added the recordedseek table. If
>     you were previously using a version old enough that it did not have
>     recordedseek, then in the current version you will have a lot more
>     database activity as there are constant writes to recordedseek as each
>     recording file grows in size.
> 
>     On the other end of things, have you tried getting a better signal in
>     the tuners by directly connecting only one HDHR to the aerial (no
>     splitter, with and without the amplifier)?  Does that help get a good
>     recording?  Are the aerial cables in good shape and solidly connected?
> 
>     Is the splitter failing?  Is the amplifier failing?  The TV is getting
>     twice the signal of the tuners, as they are dual tuners and have an
>     extra splitter.  So the TV signal may be fine, but that is no
>     indication that the tuners will be.  And the TV tuner may be more
>     sensitive than the HDHR tuners as well.
> 
>     Best practice with HDHR tuners is to have them on their own subnet
>     connected to a separate Ethernet port on the MythTV box.  But there
>     are many people using them happily without doing that.
>     _______________________________________________
> 
> 
> As you know, I had a disk failure on my Mythbuntu 8 machine.  I did not 
> migrate any files or databases to the new machine.  It is a straight 
> Mythbunty 16.041 install with no intervention on my part.  I got 
> whatever partitions it selected and nothing was carried over. We just 
> lost a few shows we wanted to watch but found them online so it wasn't a 
> big deal.
> 
> The antenna, cable, connectors are all professional quality.  The HDHR 
> reports 100% signal strength.  I don't think that is the problem.
> 
> My next experiment is recording without mythcommflag running.  I 
> strongly suspect that is the problem. I will post the result of whatever 
> tests I run tomorrow.
> 
> New problem.  On MythWeb, the left column shows small screen shot out of 
> whatever show was recorded. The oldest show is August 29 and there are 
> 52 recordings that show the clip, then 2 that do not, one that does and 
> all 4 from today are without the clip.  Not that important but what is 
> going on? And don't forget that the progress bar is missing.  I think I 
> need a new disk and new install.  Random things are happening.  It is 
> near Halloween so maybe it is ghosts.
> 
> Question.  If I get a new HD and install Mythbuntu 16.04.5 on it to 
> start over, how should I set up the partitions?  A 1T HD is more than 
> big enough for what we do so it is not a big expense, just another time 
> sink.
> 
> I do not understand your comment about recordedseek.  Where do you see that?

recordedseek has been there 'forever.'   I posted a predecessor of my 
MythDVBcut script, which used it, in  ~ 2010.  For mpeg2 recordings, anyway.

> 
> Allen
> 
> 
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