RAID-5 vs RAID-50

[ddrueding]

I know RAID-50 is supposed to be faster, but what if the computations are happening on a dedicated card (specifically my 3Ware 9650SE)? From what I understand, reads from RAID-5 are essentially as fast as RAID-0 anyway (the data is striped, but to one less drive) and writes are limited to the power of the on-board processor. If this were the case, than RAID-50 essentially gives the processor 2 calculations to make instead of one for writes, and one less drive in the striped read.

I've been doing some googling, and will continue to post the results of my research (and potential testing), but was curious what people here had come up with.

 

[timwhit]

Maybe you need two controller cards? Will that work?

 

[ddrueding]

That would work, but I'm looking for the most performance with what I have. Besides, I'm out of PCI-E slots

 

[blakerwry]

RAID50 involves no more parity calculations than RAID5. You simply have more raw disk speed to work with. If your bottleneck is your controller at all times, then there's no point obviously.

RAID5 (or 50) advantage over RAID10 comes with the overhead needed to maintain redundancy. RAID5/50 only has a 1 disk overhead. RAID10 has 100% overhead. If you can afford 100% more disks, simply go with RAID10 -it'll be faster, simpler, and more redundant.

 

[ddrueding]

Well it doesn't look like the 9650SE supports online capacity expansion with RAID-50, so I'm ruling it out for technical reasons. After I get my data off I still might test it. Looks like another day or so...