[mythtv-users] RAID 1 mirror with mythtv backend???

[Nikolai Lusan]

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Greetings,

As others have said in reply to your post, mythtv should not cause issues
with RAID - or any FS for that matter. That is not how it is accessing the
drives, it's doing it through an abstraction layer on top of RAID/FS.

These days most of my machines are ZFS using mirror VDEV's in multiple VDEV
pools ... with the exception of my mythtv box. I recently upgraded the
hardware on my mythtv box (and did a fresh install) as it had been stagnant
for over 10 years - I kept the same tuners and IR receiver, so I was able
to fudge things like the config.xml so I didn't have to completely setup
mythtv from scratch. I chose not to put ZFS on this machine because there
is really no benefit in it's advanced features for mythtv (unless you
_really_ want to keep those recording files in a backup somewhere using ZFS
snapshots and remote send/receive to another pool [on another machine]).

The main reason for choosing a specific RAID and/or filesystem setup is
going to be speed. I run my DB on a different host, and the media PC is a
slave backend - it's also the primary frontend. I have chosen to go with a
RAID0 setup on my new hardware, these days I am almost allergic to single
spindle installs, and I have noticed some performance improvements in
LiveTV playback - less skipping when one program slot ends and another
begins.

Considering everything if I were running a monolithic myth setup I would
have the primary OS and DB on ZFS with mirror VDEV and a minimum of 4
drives (2 vdevs) in the pool - this is equivalent to a RAID10 setup giving
redundancy, and speed (plus ZFS can compress many of these files on disk
increasing storage space). For the recoding data and metadata files I would
play it fast and loose with RAID0+LVM+ext4 - it is, after all, bulk data
that can be replaced. Bulk video (i.e. any DVD/Blu ray rips and/or
Downloads) is up to you - you could put it on a pool with some redundancy,
or not depending on how much you care about that data.

In many cases the choice of RAID, LVM and filesystem are personal tastes -
although there is some evidence out there for performance gains using
certain mixes for different tasks.

Remember non-zero RAID only provides redundancy, not backup, and not all
filesystems are equal. Also keep in mind that there is not much software
out there accessing drives at a low level, so it's not likely to be
software causing hardware issue, but it could be a file system issue
depending on how the FS is tuned and how the RAID array is addressed.


- -- 
Nikolai Lusan <nikolai at lusan.id.au>
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