[mythtv-users] Some master/slave backend advise required

[Jean-Yves Avenard]

On 3 June 2014 04:59, Johan Van der Kolk <johan.vanderkolk at gmail.com> wrote:

> I can see two issues now:
> Bandwidth: When recording 10 channels (what I want to achieve), I estimate worst case (based on what i recorded so far) 3GB per channel per hour, or 833Mb/s one way traffic, without other overhead. And not watching anything...
> How to solve this, and does myth traffic between master and slave benefit from Jumbo Frames. I could use two network cards in each machine, and create a 2 x1 Gb trunk between the switches.
> Second part of the problem might be that the ZFS file storage is not fast enough. (upgrade to SSD maybe)

what are you using was your ZFS storage?

if using FreeNAS , they have heavily tweaked their ZFS component, and
anything less than 8GB will give you poor performance.

At the price of RAM these days, just throw more RAM at the thing, 16GB
will be plenty for most usage

In regards to the CPU usage, one of the core issue is that myth writes
to the database during every recordings, very often. In 0.27.1 things
were greatly improved, but fundamentally, it still write as much to
the database as it used to.

One of the first thing you should try is store your DB on a separate
SSD, and not using ZFS...

I run a similar setup as you, and 800Mbit/s is no problem over gigabit
in actual usage, and the ZFS array handle this just fine (I achieve
over 95MB/s over NFS), a tad more over CIFS, and I maxout the gigabit
link using myth:// protocol (which unfortunately at this stage you
can't use for writing recordings to disk)

My storage is running FreeNAS on an i3-4130 (3.4GHz dual-core), 32GB
of ECC RAM and 6x4TB in RAIDZ2 config (disks are AES256 encrypted). I
chose that i3 because it's the cheapest CPU giving me AES hardware
acceleration and ECC support)

My backend is a Xeon E3-1220v3 quad-core, with 16GB of ECC RAM, that
link to the freenas box over a dedicated gigabit link (with jumbo
frames on)

all works brilliantly (though it took a lot of hard work and fixes to
get mythtv to do things properly, and is the core reason we have
0.27.1 today)