HBA Multipath RR or MRU

[zenomorph]

Hi there,

We'd like some advice on best setup for HBA multipath. We have 2 Vmware ESXi 4.1 clusters connected to different storages HP EVA and another cluster EMC VNX.

At times the ESX hosts can be running quite high loads in terms of I/O and were looking what to set for the multipathing policy to improve performance. Currently were running the default MRU on both clusters. But can anyone give some advice if I sometimes have high loads on the ESXi hosts would running RR multipath improve performance and throughput on the ESXi hosts?

Obviously if I were to run Powerpath VE that would be the most ideal but given the number of hosts we have and the software costs heaps $$$ at this point in time its not an option.

Many thanks....

[Gkeerthy]

the entire multipathing decision is relied on the type of the storage array, if you have Active/Active array you need to use round robin, and if you have Active/passive you need to use Fixed, for active/passive if you select round robin you will end up with LUN trashing.

you need to check with the vendor documents and their best practice. I believe the EMC will be Active/Active, power path is good, but the default vmware multipath module is equally good.

So for Active/Active RR is the best

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=101134...

[UmeshAhuja]

Hi,

Round robin would be the best option for both the storages.For more details you can go through the below links

FOR EVA

http://www.ivobeerens.nl/2010/01/19/best-practices-for-hp-eva-vsphere-4-and-round-robin-multi-pathin...

FOR EMC

http://www.boche.net/blog/index.php/2010/02/04/configure-vmware-esxi-round-robin-on-emc-storage/

[zenomorph]

Guys thanks for the reply, as of now we have already configured our EVA storage to use RR.

However reading more documentation on the VNX raises more confusion as I've looked at the VMware hcl and it shows the following to use the "FIXED" policy rather than RR.

Many thanks,

[mcowger]

The question of Fixed vs. RR on VNX is an open one.  I'm speaking here as an EMC employee (which I dont ususally do):

Round Robin will generally give you better overall performance, and shorter queues and better throughput/performance.  However, there is a small issue with RR and VNX in the case of a NDU or SP reboot.  If an SP reboots, the path selection plugin will start using only a single SP for everything, and wont automatically failback and 're own' the LUNs on the recovered SP.  Most of my customers understand this and are OK with the fact that after an SP reboot (either due to crash, failure or upgrade) that they will need to change the default own of their LUNs.

Fixed pathing doesn't have the ownership change problem described above., because it will always go back to the owning path on recovery.  However, it doesnt have any of the performance benefits of RR.

So, use whichever one meets your needs.

Worth noting that this RR behavior with VNX will be changing in the next version of vSphere

[mcowger]

you need to check with the vendor documents and their best practice. I believe the EMC will be Active/Active, power path is good, but the default vmware multipath module is equally good.

NMP / RR is not equally good to PowerPath.  Path identification, recovery time, throughput and IO/s, path balancing are all improved over NMP/RR.  Most PP/VE users report a 2x improvement in response time and throughput.