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May 14th, 2013 06:00

Equallogic volume distribution

Hi all,

I have an Equallogic group with two PS6100's and two PS4100's working together. I was always under the impression that volumes would be capacity load balanced across 3 members maximum based on official documentation (note it says 'under normal circumstances') however on this particular installation I am seeing several volumes that are spread across 4 members which is a surprise to me. Can anyone tell me why I am suddenly seeing it load balanced across 4 members?

Note: I just recently joined the two 4100's in to the 6100's group and one of the 4100's is still performing its RAID verify.

Thank you!

18 Posts

May 14th, 2013 08:00

I agree its probably re-balancing. Will need to see how this changes over the next few days.

I checked the ISL which is 2x1Gbps in a port channel and we're only seeing approx 100Mbps between the two storage switches so I have no concerns there.

18 Posts

May 14th, 2013 11:00

There are two Cisco 3560E's dedicated to servicing 2xPS6100's and 2xPS4100's in a full mesh topology, with all connected hosts uplinked to BOTH switches. There is no case where the only path between a host and the storage REQUIRES the ISL (unless there was a NIC failure on a host). I was under the impression that if the ISL ever became oversubscribed and latency increased due to TCP retransmits or pause frames that MEM or Dell's DSM would be able to NLB the sessions accordingly.

It's a difficult statement to back up if there are zero indications of an oversubscribed ISL. Packets per second, megabits per second, interface statistics, buffers, etc, are all well within normal parameters.

18 Posts

May 14th, 2013 12:00

I messed up the diagram a little bit when it comes to the active/inactive ports on the PS6100's but you get the idea. 4 active and 4 inactive ports to each switch.

18 Posts

May 14th, 2013 12:00

We are distributed correctly for HA.

I drew up a quick diagram:

http://i.imgur.com/HmyAtuJ.png

18 Posts

May 14th, 2013 13:00

I'm glad that clarified that. You had me a bit worried even though I was sure it was sufficient (for now). :).

I'll keep an eye on the volume load balancing.

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