[mythtv-users] question about RAID

[Steve Adeff]

On Sunday 08 January 2006 19:50, Gavin Haslett wrote:
> RAID 0 would be a straight stripe with no data protection. You were
> talking about three drives, so in order to use all three you'd be
> talking this or a RAID 5 in order to get some modicum of protection.

I was under the impression RAID 0 was the fastest RAID, but has no data 
protection? Is there no way to get RAID 0 to use more than one drive? Like I 
said, I'm not concerned with redundency on the RAID0 since I plan to save 
recordings I want to keep to a RAID5 array. 

> If you wanted to go RAID 1 or RAID 0+1 then you'd need an even number of
> drives, and total capacity would be half the actual aggregate capacity
> of all those drives.
>
> Note that in order to create your RAID you're going to have to re-
> partition your existing disk... so a backup and restore is inevitable.

My plan was to use the two new drives to setup the RAID0, copy the files over 
from my current drive, then remount everything so that the RAID0 becomes my 
recording directory.

> I know you said data protection is not an issue... but believe me when I
> tell you that it can become an issue rapidly. You can build a
> significant collection of recordings on any reasonable size media (I
> have mirrored 160Gb drives myself), and there's no recovery if you lose
> a single disk. It's not like you can cut the array down to half the
> array and still get half your data back... you'll lose it all if one of
> the drives in a RAID 0 fails. RAID 5 and RAID 1/0+1 would at least allow
> you protection.

Which is why I plan on a RAID5 for my archives drive. I'm hoping HD-DVD makes 
a large presence upon its release and I can just buy the shows I keep in 
HD-DVD and not need to archive them for a long time.


> >From a sheer cost perspective I'd say RAID 5 is the way to go... but
>
> bear in mind that the processing overhead of RAID 5 plus the data load
> of reading and writing data and parity in a RAID 5 will make it slow,
> especially since you run significant risk of saturating the PCI bus with
> SATA.
>
> My dual 160's work great for me right now, and if I wanted to expand I'd
> just add another pair of drives and continue my RAID 0+1 I set up. I
> have thought about buying a third and going RAID 5 (would double my
> storage). Since I'm running ATA133 instead of SATA (drives were cheaper
> at the time) I am not really stressed about saturating the bus... but my
> poor old AMD 800 might not be happy with me ;)

-- 
Steve