[mythtv-users] backend storage performance needs?

[Jan Ceuleers]

On 19/05/2020 12:44, Jim Abernathy wrote:
> Since SSDs and RAID is not recommended, I avoided that in the discussion.

Not sure why SSDs aren't recommended. That's the way I've gone and it
sidesteps many (all?) of the issues Stephen listed.

They of course introduce other issues, such as cost, but they also have
tremendous benefits such as no noise, low power consumption, low heat
dissipation, etc. I'm not listing raw sequential speed here because
that's not needed for a MythTV backend, but essentially-zero seek time is.

It does make sense to limit needless writing to SSDs, but their
endurance has improved to the point where that may also no longer be
necessary. Things like mounting with noatime,nodiratime options. The
machine is also on a UPS so I furthermore bunch my writes (minimising
the probability that slow sequential writes to a file result in blocks
being written and rewritten) by mounting with barrier=0,commit=60.

My backend contains a load of SSDs (14TB worth), which are
SATA-connected to the motherboard and to an additional PCIE SATA
controller. That's another SSD disadvantage: they don't come in high
capacities (at least not at affordable prices).

The database resides on a RAID1 pair consisting of partitions that sit
on SSDs from different manufacturers (thereby hopefully minimising the
probability of near-simultaneous failure).

I have six tuners (two HVR1950s and one 4-tuner HDHR).

I built this machine about a year ago, and so far only 1% of the SSDs's
write endurance has been consumed. That includes all of the writes that
were necessary to migrate content from the predecessor server to these
SSDs. At this rate write endurance won't be the reason why I retire the
machine.

HTH, Jan