Since Windows 2008 R2 it is possible to build an Hyper-V cluster with Cluster Shared Volumes (CSV). One way to build suge a cluster is to use Equallogic PS series.

With atleast firmware 4.3.5 there is an issues when you create an Failover Cluster for use with Hyper-V with the following configuration:

- More then one PS series Equallogic
- More then 2 NIC’s per node
- More than 4 nodes
- More then the default MPIO HIT kit which is 2.

All has too do with how Equallogic handles Peristent Reservations (PR). Per CSV there are only  max. 32 PRs available. But how do they get this number? My assumption is the following formula:

Number of Equallogics   = E
Number of NICs    = N
Number of MPIO    = M (default HIT = 2)
Number of Servers   = S

E * N * M * S = 32

So for instance if you have 2 Equallogics, 2 NIC’s per node which is the minimum, the default  HIT kit settings of 2 and 4 nodes you will end up with the following:

2 * 2  * 2 * 4 = 32

Why did I use this example. This because with 5 nodes the failover cluster will fail when ever you want to do a storage migration or an reboot of one of the nodes. This is because you will have 40 PR’s! This all is with firmware version 4.3.5.

Now, is Equallogic doing nothing to fix this because a Hyper-V cluster can contain a maximum of 16 nodes. With the formula from above you will get with the use of only 1 Equallogic atleast 64 PR’s (1 * 2 * 2 * 16). But why build a 16 nodes Hyper-V cluster with only 1 Equallogic PS series? You will probably use atleast 2 maybe 3 arrays.

Equallogic has released a firmware version 4.3.5 Patch L1 which you can get here. If this will fix the issue with the limited number of PR’s I don’t know. What I also don’t know is if this Patch L1 includes the Patch H1 which I received from Equallogic support which fixed my problems with my 7 nodes, 2 Equallogic, 2 NIc’s per nodes and default HIT kit settings Hyper-V failover cluster. What do I know? Firmware 4.3.5 patch H1 fixed my problem, but rumours are that this only allows 96 PR’s.

This 96 PR’s will get you this:

E * 2 * 2 * S = 96

This leaves you with 24 to be made up out of (the 2 NIC’sS and 2 MPIO’s are a minimum) :

2 Equallogics and 12 nodes
3 Equallogics and 8 nodes
8 Equallogics and 3 nodes
12 Equallogics and 2 nodes

Hopefully Equallogic will enlarge the number of PR’s per CSV to atleats support the maximum number of arrays in a group which is I believe is 15 and with the maximum of 16 nodes in a Hyper-V Cluster . With these numbers and the default of 2 NIC’s and 2 MPIO’s the PR number must be 960 per CSV!

This article is also posted on Dell Tech Center with some interesting comments!

This artcile is based on my personal experience with Equallogics and is in no way supported by Equallogic or Microsoft. I’m still waiting on an answer how the PR number per CSV is calculated.

Tags: Cluster Shared Volume, CSV, Equallogic, firmware, Microsoft, SAN, Windows Server 2008 R2