RAID Level 55

[Chuck Swiger]

Nikolas Britton wrote:
> I was reading on wikipedia about RAIDs trying to pass the time and I
> was thinking why not have RAID 5+5 or 5+5+5 levels, sure you waste
> 2/3th's of your space but wouldn't this be a killer setup for a
> directory server where fast reads are of the utmost importance?

Actually, no.  RAID-5 prioritizes cost and reliability at the expense of 
performance.  RAID-5 does adequate for read-mostly volumes with big files, and 
does worst with lots of writes to small files.

RAID-5,0 or -1,0 would be a much better choice.

> Would you add up the transfer rates for each drive to get the total
> transfer rate of the array?, if true you could easily saturate a 10
> gigabit ethernet connection with a 555 array of IDE or SATA drives.

Nope.  Most machines are limited by their PCI bus and chipset to less than 
1Gb/s of backplace bandwidth, although the higher-end boxes with multiple PCI 
busses or PCIe will do better.

-- 
-Chuck