[mythtv-users] Another take on large-capacity disk enclosures

[Yan Seiner]

On Mon, June 15, 2009 2:23 pm, f-myth-users at media.mit.edu wrote:

> The plan is to use the disks as a JBOD (and in fact most of them will
> be sleeping most of the time, so the two cards' performance with many
> disks active should be irrelevant, and means that, while a power
> supply that can handle the peak is advisable, it will be quite
> unloaded most of the time [are 80+'s still efficient with such low
> loads?  haven't checked recently]---I'd rather not get fancy with
> multiple power supplies and something to switch 'em on/off).  I'm
> also thinking that, unless the NAS mobo gets other duties, it might
> spend most of its time with its CPU throttled (and -maybe- sleeping
> if the stars align and that's reliable and fast to resume).

Practical considerations:

It takes a desktop-class system about 6-10 hours to check a 2 TB raid-5
array.  You really don't want a single large array comprising of 20 1.5 TB
drives; fsck would take weeks.

If you pick your hardware right, you can get by much cheaper with esata +
port multipliers at little to no performance penalty, especially if you
design the wiring so that drives on the same port multiplier are in
different logical groups.  Port multipliers come in 1x5 versions, so 4
esata ports == 20 drives.  See the sata maillist for hardware that works.

A single moderate PS will easily handle 20 drives; that's only 200W load
max.  Even at startup, you're only talking maybe 300W to spin up all the
drives.

--Yan