Posted by rcamarda on 05/18/06 14:23

Raid 01 should be faster than raid5

1. Raid 5 has to calculate the xor'd data
2. raid 5 has to do 2 writes (1 for the actual and 1 for the xor'd
data)
3. Raid 5 will be slow in a degraded array, more drives the slower it
becomes
(If a drive fails, it will have to read all the other data, pulls
the xor'd data to recreate the missing piece. 10 drives, 1 fails, all
drives have to be read)
4. Raid 5 upside: disk efficiency. You only lose 1 drives capacity for
redundancy (Note: I didnt say you use one drive for redundancy, just
its capacity). More drives you have, the more efficient the storage (3
drives yields 66% capacity. 10 drives yields 90% capacity)
5. Raid 0+1 still has two writes, but it does not have the overhead to
calculate the xor'd data
6. Raid 0+1 does not suffer ill effects if one of its drives fails.

Normally, Raid 0+1 should blow the doors off of Raid 5, shouldn't
even be a contest. Raid 5 is great for mostly reads and where
performance is not critical if the array is degraded. Raid 0+1 is
faster, but more costly since you get only 50% capacity of the total
disk storage.

It's worrisome to me, thinking I might have one of these controllers in
my HP machine (HP bought Compaq...anyone know if HP uses the LSI
controllers?)

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