iSCSI performance

digitaldentistry wrote:
How is the performance of Pro2 in RAID 1 compared to say SATA drives on a Dell PowerEdge T310 running in RAID 1? I have tried doing some research online but can't find any performance testing results and data. This is in an environment where there are many small file reads and writes on a 200 to 300GB data set.

Well, I just tested a T310 with a Dell SAS 6/ir controller and two 500GB SAS Seagate Barracuda ES.2 drives (7200rpm) and it topped out at 120 MB/sec in linear transfer speed. That's pretty much the speed of the disks.

iSCSI performance on the Pro, well I don't have the Pro, but I have the Ultra 2. There is some serious overhead in the iSCSI department, I think, and it shows in the official numbers as well; a single drive which will give me 100MB/sec attached directly to SATA will deliver 60-70MB/sec in the Ultra 2 over iSCSI. Access time (seeks) is not affected at all. That's good enough for lots of things of course, but personally I don't think these devices are up there with a real server -- yet (they will be though, and they are better for a few specialized things).

That SAS 6/ir isn't very impressive either, a real RAID controller with a real array (meaning, more spindles in level 5/6 or even 10) will easily deliver several hundred MB/sec... but then the problem becomes more "what to do with all that data"? Which interface to fill it with?

I'd say a T310 in pretty much any configuration (even using Windows built-in software RAID) will absolutely smoke a Pro 2, but price, power requirements, cooling requirements, ability to easily replicate to another identical NAS (two units will still not even approach the price of a server) is in the NAS' favor.

Horses for courses and all that. 8)