[mythtv-users] recommendations for building new FE/BE HDTV system?
beww at beww.org
Sun Apr 5 18:48:55 UTC 2009
On Sunday 05 April 2009 12:31:19 David Brodbeck wrote:
> Tyler T wrote:
> > That's basically what I've done with some old PATA drives. 16GB Raid-1
> > for the OS, then a second partition on the first drive for NAS --
> > which is backed up nightly to a sister partition on the second disk
> > (because Raid-1 is NOT a backup!). Then the rest of each drive is
> > Raid-0 for recordings. Works great, although you do take a small hit
> > on the extra power consumption.
> Why are you using RAID 0 instead of Storage Groups? (This isn't a
> criticism, I'm genuinely curious.) I would think Storage Groups would
> be a bit more reliable -- losing one drive would take out half your
> recordings, instead of all of them.
One word: Performance.
I don't mean to answer for the person to whom the question was directed, but I
can tell you why I use RAID0 instead of Storage Groups.
RAID0 will increase the performance of the disk system, while Storage Groups
(or LVM) will not. Note this example (sda is a single drive, md1 is a
two-drive RAID0 array:
Timing cached reads: 1822 MB in 2.00 seconds = 911.75 MB/sec
Timing buffered disk reads: 174 MB in 3.00 seconds = 57.98 MB/sec
Timing cached reads: 1798 MB in 2.00 seconds = 899.41 MB/sec
Timing buffered disk reads: 522 MB in 3.00 seconds = 173.98 MB/sec
I'm not sure why the RAID array is more than twice as fast as the single
drive, but it appears to be, at least according to this somewhat limited
I understand that using the 2 drives in RAID0 doubles my chances of losing
data to a drive failure, and that a single drive failing will cost me ALL the
data on the array, but I'm willing to put up with that. The array is backed
up regularly, and I like the performance bump.
In fact, with most Myth systems, a single drive is fast enough, but the
improvement is real and significant.
beww at beww.org
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