Yesterday I received an email from someone. He wanted to know why he was limited to using either the “fixed” or “MRU” pathing policy for the LUNs attached to his MSCS cluster. In his environment they used round-robin for everything and not being able to configure all of them with the same policy was against their internal policy. The thing is that if round-robin would be used and the path would switch (by default every 1000 I/Os) the SCSI-2 reservation would need to be re-acquired on this LUN. (MSCS uses SCSI-2 reservations for their cluster devices) As you can imagine that could cause a lot of stress on your array and could lead to all sorts of problems. So please do not ignore this recommendation! Some extra details can be found in the following KB articles:
After the whole MSCS’ed vCenter support discussion VMware Technical Marketing reached out to me. Lets be clear, the intention of this article is not to change support. The intention of this article is to get an idea of how many of you would be interested in seeing a whitepaper on vCenter resiliency with MSCS/VCS which could be supported on best effort by GSS.
I was asked to figure out what would most interest you. I appreciate any comments around this but specifically would love to have answers on the following:
- Based on which technology would you prefer to see a whitepaper? MSCS or Veritas Clustering?
- Would you be looking for a total solution including VMware Update Manager and Orchestrator or just purely vCenter Server? In case of the total package, why?
- Are there any other components that would need to be included in a whitepaper?
Again, any help / answer / comment is very much appreciated.
We(VMware PSO) had a discussion yesterday on the fact whether it’s supported to have MSCS(Microsoft Clustering Services) VM’s in a HA/DRS cluster with both HA and DRS set to disable. I know many people struggle with this because it doesn’t make sense in a way. In short: No, this is not supported. MSCS VM’s can’t be part of a VMware HA/DRS cluster, even if they are set to disabled.
I guess you would like to have proof:
For ESX 3.5:
Page 16 – “Clustered virtual machines cannot be part of VMware clusters (DRS or HA).”
Page 11 – “The following environments and functionality are not supported for MSCS setups with this release of vSphere:
Clustered virtual machines as part of VMware clusters (DRS or HA).”
As you can see certain restrictions apply, make sure to read the above documents for all the details.
When reading several SRM docs I was wondering if Microsoft Clustering was supported or not. I knew that in version 1.0 it wasn’t supported. When reading the Release Notes I noticed the following:
Full Support for RDM devices
SRM now provides full support for virtual machines that use raw disk mapping (RDM) devices. This enables support of several new configurations, including Microsoft Cluster Server. (Virtual machine templates cannot use RDM devices.)
Microsoft Clustering Services is supported as of Update 1. But you will need to keep in mind when creating your Recovery Plan that all nodes of the cluster will belong to the same Protection Group and can possibly be started up or shutdown at the same time….. I haven’t configured SRM in combination with MSCS so far, if any of you has any tips/tricks let me know.