ESXi 4.1 and Drobo Elite bad performance?

[BradI100]

I have been fighting a Drobo Elite 800i unit for several months trying to get satisfactory performance. It is currently connected via iscsi to my ESXi 4.1 host. My host is a Dell R710.

I've followed Drobo's manual, gotten their tech support to look and they confirm it is set up right. Even had a VCP look over my shoulder to make sure it was right.  I can see all the LUNs from vsphere, and mount volumes to guests, etc. etc.

The problem is the performance is terrible. While burst speeds seem fantastic, I average 4-6MB/s on random read/writes, file copies, etc.  I've run countless tests that show the read latency is central to the problem.  It is set up for Jumbo frames. I've confirmed the vmknic, vswitch are also set to Jumbo frames too.  Also, per Drobo support I have the Elite unit connected directly to the server's onboard NIC cards to eliminate any loss from a hardware switch.  However, I did test it configured to a 1GB switch w/jumbo frames, different subnet etc.  The performance is worse when connected to an external switch.

I've tested this every which way to Sunday and still the performance is bad.

Any ideas on how to get this working right?  Is it even possible?

[BRiley1]

What's it look like if you hook the Drobo to a non-ESXi host?  Run IOmeter from there.  Maybe even see if it will recognize it via USB just to see if the may be an issue with the interface.

[DSTAVERT]

You should also consider NOT using Jumbo frames. Jumbo frames don't usually result in better performance --certainly not a significant change-- but any misconfiguration or mis optimized MTU setting will casue performance problems.

These small devices aren't particularly suited to Virtualization. In most cases they don't have very large write caches and the cache is either disabled by default for virtualization or it is recommended that it be disabled for safety.