How does the LeftHand SAN perform in a Production environment?

Solution 1:

I got several of 'em on HP hardware about a year ago for performance benchmarking testing, and some of the same things I said in the LeftHand VSA SAN question apply here too.

At the time, LeftHand's iSCSI multipathing wasn't truly active/active. Say you have:

• Four LeftHand servers with 2 1gb network cards each
• One volume on the SAN for your SQL Server data files
• One volume on the SAN for your SQL Server log files
• One SQL Server with four 1gb network cards dedicated to iSCSI

When you run a query on the SQL Server that accesses the data files, you will only get 1gb of read throughput despite the fact that you're using four network cards. The LeftHand devices (and indeed, all of the iSCSI SAN gear I've seen) will only send data from the SAN to one specific MAC address on the SQL Server.

You can work around this by:

• Using multiple data volumes and log volumes, and manually managing which path is the "primary" path for each back to the server. Even then, you're still only going to get 1gb of throughput for each data file, which restricts your backup performance, DBCC performance, etc.
• Using 10gb Ethernet.
• Using network teaming software that actually works. I've tried using a couple of vendors, and I haven't seen them overcome this problem yet.

If you need more than 1gb throughput, then until you hear from someone who's actually pulled it off, and can show it to you (not just say "oh yeah it works great on my l337 b0xx0r") then don't invest your money.

Fiber channel isn't necessarily different: it's just that you can easily get 4gb fiberoptic connections instead of 1gb Ethernet. You still have the same pathing challenges. I'm doing a presentation on this next week at IndyPASS, coincidentally - if you're in the area, swing by.