1 vs 2 vs 3 iSCSI paths; performance swing

[jenksdrummer]

Below is a set of tests I've done and the results where 1 iSCSI link/path was used, then 2, then 3. Mainly I was curious if I was tapping out on 2 links; so after adding a 3 link and seeing the bandwidth go up, and the IOPS go down (for the most part), I thought I'd test with 1 link/path. A bit surprising, all the tests under 16K (before bandwidth starts becoming an issue) show a quite a boost over 2 links, let alone a significant boost over 3 links.

Of note, all three links are 10GB on separate VLANS; all three paths are centered over 3 different switches (IE, VLAN "A" exists on switch "A", B on B, C on C though the switches are interconnected/managed otherwise).

I can give more details to the test parameters if desired; but this is about as "all things being equal" as possible.

IOMeter used; the naming is relative to the profiles used. IE, 512 R is 512 100% Read 100% Sequential. 512 W is 0% Read 100% Sequential; profiles used are unmodified.

 

[jenksdrummer]

All that and no responses...then reading my post today I realize I didn't ask the question!!!

Curious; this trade off between bandwidth vs IOPS; with IOPS notably higher with less links/small transactions...leads me to believe perhaps there are some missing optimizations or is this just a general performance drop based on (more or less...) reassembly?