SAN question

steinooo · 13 Nov 2009 at 16:01

hi all,

i'm a newbie when it comes to sans but what i'm trying to get my head around is the bandwidth that runs between the SAN and the server to which it's attached.

If we were to have an iSCSI SAN with 2 x 1Gb/s ethernet leads going from the SAN to the server, I'll get a maximum theoretical bandwith between the two of 2Gb/s = 250MB/s.

Now I've read that SAS drives give a throughput of 300MB/s, so what I can't understand is if one of the many SAS drives was being hammered at 100%, surely the link between the SAN and the server won't be fast enough to realise the disk's max throughput?

Can someone advise please?

steinooo · 13 Nov 2009 at 16:18

See that's what I've always just automatically thought, on the basis that Fibre @ 8Gb/s > any ethernet speed that is affordable...I'm getting some quote at the moment to see just how much I'd save with iSCSI over FC.

I still can't quite satisfy my own mind though, because if there are for example 12 hard discs, the maximum bandwidth from them is surely 12 x 300MB/s, which is far more than can be handled by even FC?

steinooo · 16 Nov 2009 at 11:04

bigredshark said:
I've run big exchange installations (1000 user +) on 2x1GBit iSCSI and the throughput was never a problem (IOPs were, even with 120 odd SAS disks).

thanks for that, that's interesting. Did you find a solution to that?

steinooo · 16 Nov 2009 at 11:22

I see thanks.

A few more if I may : If I was to get dual controllers, can one controller only see one set of discs, and the other controller see another set? Or can dual controllers both see all available discs?

steinooo · 16 Nov 2009 at 12:04

Right, is this just an option you can set when you set it up then presumably?