RAID suggestions...

[Bill Davidsen]

Ashley M. Kirchner wrote:
> 
>    I'm looking at setting up a RAID system for doing video work.  My two 
> main requirements are speed and reliability.  Speed is an issue because 
> of the constant streaming of hundreds of megabytes, if not gigabytes of 
> data that is inherent with video.  And obviously reliability, I want to 
> make sure I don't lose any data of a drive crashes on me.  This will 
> also be a hardware RAID solution (as opposed to software) and, depending 
> on funds, I may try to make it a hot-swappable system.

fast - reliable - inexpensive. pick two.

But unless you are running multiple video feeds into the disk at one 
time, fast isn't an issue. Commodity SATA drives will do 50MB/s without 
effort, and 200MB/s is readily reached using software RAID. If you want 
fast and reliable, go SCSI. Until recently I ran 20+ servers for an ISP, 
with 6M users, and 2-6TB/server. There isn't a non-SCSI RAID card I can 
recommend (that does NOT mean they don't exist, I just didn't find one).

If 150MB/s write and 200+ read with good reliability will do, go 
software RAID-6 for the data, RAID-1 (three way if you're paranoid) for 
the o/s and swap.

Hardware RAID is very good, but the "firmware RAID" on motherboards and 
cheap controllers are not usually fast OR reliable enough. Use a lot of 
memory. No, more than that.
> 
>    Based on all the different RAID levels out there, what does the 
> collective suggest?  1? 3? 5? 0+1?
> 
cheap: RAID-5
reliable: RAID-6+hot spare
fast and reliable: RAID-10+2xhot spare, RAID-1 for bot/root/swap

For SCSI I have had good luck with the "ServeRAID" IBM controllers. 
They're Adaptek with IBM firmware hacks, I believe.

-- 
Bill Davidsen
   He was a full-time professional cat, not some moonlighting
ferret or weasel. He knew about these things.