[mythtv-users] Wiki: Balanced Disk I/O

[Gary Buhrmaster]

On Tue, Aug 11, 2015 at 3:48 PM, Peter Bennett (cats22)
<cats22 at comcast.net> wrote:
> Hi MythTV experts
>
....
> Does anybody have an opinion on this?

While the recommendations do not reflect current hard drive
capabilities, the theoretical maximum transfer rates are just
that, theoretical.  The limiting factor in hard drive performance
is much more likely to be seek time (which has not changed
substantially in over a decade) than raw media streaming
transfer speed (which have nothing to do with interface speeds)
for typical MythTV usage.

Some file systems will (attempt) to optimize the allocations
to minimize seeks, while others do not.  If each I/O op
needs to access a random block on disk (along with the
file metadata), you can easily see 100% utilization on
only a few Megabytes/sec, which would have poor results.

And that does not count the need for certain synchronous
operations which requires all pending activity to wait for
completion.

So, while, on average, the recommendation is no longer
needed on many recent generation solutions, any
particular system will vary.

I think it may make sense to place such information
into an "advanced tuning" section rather than mainstream
recommendations, since it will be needed by some
some of the time, while overly complicated the simple
cases.