[mythtv-users] Partitioning advice request

Mike Perkins mikep at randomtraveller.org.uk
Fri Apr 15 10:31:28 UTC 2011

On 15/04/11 01:54, Raymond Wagner wrote:
> On 4/14/2011 18:36, francis3 wrote:
>> Would I get any improvement dedicating a single partition to each tuner?
> Getting your root (with database) and swap off the same disk as your
> recordings will go a long way to improving performance.  The problem
> with recordings is the disk flush loop in the MythTV file writer.  Seven
> digital tuners might manage as much as 20MB/s, and while linear
> throughput of that scale is not a problem on a modern drive, the rapid
> seeking is going to severely reduce the performance.  Fragmentation is
> going to make this worse over time, but XFS with pre-allocation should
> help in this area.  A low power 5900rpm drive was a particularly poor
> choice in this regard.
> If your single drive does not meet your performance needs, the only real
> option is to buy additional hard drives.
I agree with all of the above, but surely the point of having one drive per 
tuner is that you reduce head movement - assuming mythtv is smart enough to 
spread the recordings around.

(Actually, it isn't one drive per tuner you should be aiming for, but enough 
drives to cover the maximum number of simultaneous recordings you plan to 
schedule. Not quite the same thing, given multirec and all that.)

You /must/ put your OS and database on a separate drive since the head seeking 
will interfere with the large chunks the recording is writing to disk. The idea 
is that each recording drive then just moves the heads gradually as the files 
build up == very little noise.

A much better plan, which removes all your noise considerations, is to split 
your backend and your frontend into two separate hosts connected by wired 
Ethernet. Your large, hot, noisy backend can then be stuffed into a (ventilated) 
cupboard somewhere else in your house and your low-heat, noiseless, diskless 
frontend occupies a small space beside your TV.


Mike Perkins

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