Raid-1 to Raid-5 = Speed Increase?

[gcwebbyuk]

I am currently running 2 Barracuda 7200.11 1TB drives in a Raid-1 (mirrored) array.

How much of a speed increase (if any) should I expect by adding a 3rd drive and using RAID-5.

I always use RAID-5 where possible on servers, but have never carried out any comparisons in speed - has anyone here? :shrug:

[Mr Alpha]

I haven't run any test but three drive RAID 5 should be slower than two drive RAID 1. In RAID 5 the third drive is used for parity so you are at best still reading from only two drives just like in the RAID 1. For writing to the RAID 5 you need to do the parity calculations, which will make things slower, especially for small random writes. How much slower depends on how good your RAID card is.

[gcwebbyuk]

RAID card is the standard Mobo one, so nothing fancy.

Think I will stick to just 2 drives then in RAID-1 - I don't need the extra space, just wondered if it would speed things up.

[Randyman...]

RAID-5 should improve read speeds even with onboard MoBo RAID IMO. It is essentially a 2-Drive RAID-0 with Parity as far as reads go. The Writes might be a different story as that is where the XOR Calculation overhead comes into play (a dedicated RAID card with its own CPU is ideal for RAID-5/6).

:cool:

[dorkbert]

RAID5 would improve read speed as long as the array isn't critical (one dead drive) Write will take considerable performance hit since fakeRAID on motherboard probably doesn't have hardware XOR engine, so that has to be handled by host CPU.