[mythtv-users] One disc drive seems fine

Josh Mastronarde jmastron at gmail.com
Fri Dec 23 17:52:28 UTC 2011

On Fri, Dec 23, 2011 at 6:44 AM, Paul Gardiner <lists at glidos.net> wrote:

> Just upgraded my girlfriends combined FE/BE to play HD in the UK.
> Added a Geforce 210 for playback and a PCTV 290e USB stick for
> recording. It has just one disc drive for OS and recordings.
> I expected problems, but I experimented last night. Seemed
> to be able to handle 4 simultaneous HD recordings and one playback
> with no apparent difficulty. It's just a 500GB drive, so I
> guess she might find it tight on space, but performance-wise
> it seems fine. Just thought I'd feedback to the list.

Add me to the list of those who've always run one drive with no issues, in
various sizes, since 2004 -- and the current one is a 1.5TB WD "green",
i.e. slower RPM, drive.  Current system has a dual-tuner HDHomerun
recording ATSC.

A quick search for specs for one of these WD drives shows a write bandwidth
of ~100MBytes/sec (a .  An HD ATSC stream maxes out at ~20Mbits/sec, or
2.5MBytes/sec.  Yes, thrashing with multiple threads accessing different
parts of the disk is going to reduce the actual available bandwidth
significantly, but even 2 streams recording plus 2 streams playing is only
10% of the theoretical max, which should leave plenty for database and OS
access and the switching overhead, especially with a 32+MB cache
(effectively ~12 seconds worth).

I don't doubt that systems with many more/higher bandwidth recorders or
more frontend clients could run into issues, or that overall interactive
response could be slightly better (especially if you're using the machine
for other work also) with mutliple drives, but I haven't seen any evidence
that it's *required* for a general purpose backend/frontend machine.

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