RAID 1 performance?

[KungFu-tse]

There's a lot of talk about RAID 0 here but not a lot about RAID 1.

Anyone with a RAID 1 setup? Is there a significant increase in reading speed?

 

[Peach]

Theres no performance increase, but theres probably a small performance decrease (i'm talking 1-2%) because you are writing the same data to 2 disks at the same time.

 

[ambit]

if the controller is smart enough to read from both source disks, you'll see a small read increase.
As Peach said, writes will be a little tiny bit slower.

 

[DougLite]

For server work, with a smart controller, RAID-1 can be blazing fast - each member of the array can individually service read requests. For server work with lots of small read requests over a high percentage of the physical area of the disks, this is the kind of performance boost you want. With this scheme, a RAID-1 array can literally serve two reads at once. Coupled with command queuing, RAID-1 can be a great choice for numerous, small, and random reads. On the desktop, I doubt that very many controllers seen in consumer/enthusiast systems are smart enough to allow the load balancing of reads between the disks in a manner that boosts performance. Also, write requests do tie up the whole array, so those will be somewhat slower.

 

[zandor]

I ran a raid-1 in my desktop at my old job. Good thing I did too, as one of the WD1200JB drives in the pair died on me.
Using a 3ware 2 channel controller I really didn't notice any speed difference after the 2nd drive died. That's a $100 controller or so, and a cut above your average mainboard integrated controller or cheap Silicon Image 3112 or 3114 card.
On that system raid-1 apparently did nothing in terms of speed (unless the array was rebuilding after a disk replacement, then it was slow). It did, however, give me a massive increase in reliability.

edit: Fix typo.

 

[DougLite]

I don't doubt Zandor's performance experience. Another thing to remember is that queue depths are rarely high enough to get multi spindle scaling going on a desktop.