MSCS, NLB, VmWare vSphere 5 with iSCSI SAN

[KennyView]

Dear all,

I am reading the document Setup for Failover Clustering and Microsoft Cluster Service in order to understand to design a clustered setup spread over several ESX hosts running vSphere 5.0 Enterprise.

Any idea what is the best setup?

My suggestion was:

* 2 VM's running Win2K8 R2 -  SQL 2008 R2 Active Passive cluster - vm's are running on RAID10 iSCSI box

* Present dedicated Volume via MS iSCSI initiator to 2 vm's to host SQL Database - also running on RAID10 iSCSI box

However this guide mentioned Pass-through RMD disks on clusters across physical machines and also mentioned clustering on iSCSi disks is not supported ...

Kind regards,

Kenny

[Scott Norris]

Depends what the situation is, Did you need this setup to be fully supported? in if there is issues are you going to be going to VMware for help?

If so and you want to use iSCSI you will have to setup "in guest" iSCSI software initiators which looks like what you were proposing anyway.

You are correct VMware only supports FC RDM drives for custer accross boxes, iSCSI and NFS and FCoE is not supported yet.

Below is a good guidle line document for MSCS withing ESX.

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1037959

[KennyView]

So if I understand correctly (and yes I need a fully supported setup ;-)):

* 2 VM's for SQL Cluster with MS iSCSI initiator pointing to a  iSCSI volume

* 2 VM's must be located on one ESX host

So clustering over ESX hosts will not work (or is not supported) ?

[Argyle]

If you have license for VMware HA I would re-evaluate the need for MSCS. You can lower the complexity of the solution by not involving MSCS and run your SQL servers as any other VM.

You achieve basically the same uptime with VMware HA. In an worst-case event of a power failure of a host, there will be a downtime on the SQL service, doesnt matter if its MSCS or VMware HA.

The one benefit with with MSCS is that you can do a failover to another VM server when you are patching the Operating System (the SQL service is still stopped/started and causes a short downtime). But for this you are adding more layers of complexity like MSCS itself and different disk setup and constraints.

[KennyView]

I understand however, the customer already decided to implement a SQL Cluster as backend and NLB as a frontend. Now I am looking for best practices and supported configuration specific for Vmware with iSCSI San ...

[Scott Norris]

MSCS still has its place and out of the box HA does not provide the same protection, While vSphere 5 has an application monitoring API you have to include this or the application made aware of this for it to work, correct me if im wrong. so MSCS will still protect at the application level, weathers its a failed disk, service, OS and hardware. im still a firm believer of going as native as you can so MSSQL and MSCS are made to work together.

HA or equivilant will eventually make MSCS redundent that is if MS dont make it a true cluster and have them working as one in the future.

KennyView :

If you need a supported solution the only way your going to achive that with iSCSI across different ESXi hosts is to do "in guest" software initiators

so you have your 2 VMs on any host you want, and setup software iSCSI adapters in the guest OS(Windows) and connect them to the LUNs for the shared Cluster resources.

Look it will work with iSCSI RDMs its just you wont get support if something goes wrong from VMware.

[KennyView]

When I take a look at http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1037959, I see indeed the in guest is supported

When I take a look at http://pubs.vmware.com/vsphere-50/topic/com.vmware.ICbase/PDF/vsphere-esxi-vcenter-server-50-mscs-guide.pdf page number 9 on top of the page, the document tells RDM is recommended ?

What I am missing?

[Argyle]

As I read it, RDM is the recommended one (across boxes) if you want to use a "VMware" type of shared storage. But it also states:

"Use of software iSCSI initiators within guest operating systems configured with MSCS, in any configuration supported by Microsoft, is transparent to ESXi hosts and there is no need for explicit support statements from VMware"

So both are viable. iSCSI within the guest is probably easier to manage. Go the RDM route if you have some SAN functionallity or tools like SAN based snapshots/replication that you want to use.

[Scott Norris]

KennyView wrote:

When I take a look at http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1037959, I see indeed the in guest is supported

When I take a look at http://pubs.vmware.com/vsphere-50/topic/com.vmware.ICbase/PDF/vsphere-esxi-vcenter-server-50-mscs-guide.pdf page number 9 on top of the page, the document tells RDM is recommended ?

What I am missing?

Yes RDM is definatly recommended, the issue is your using native iSCSI for your storage protocol for ESXi meaning RDMs on that storage is not supported for MSCS

from the article "Fibre Channel – Configuration using shared storage for Quorum and/or Data must be on Fibre Channel (FC) based RDMs (physical mode for cluster across boxes “CAB”, virtual mode for cluster in a box “CIB”). RDMs on storage other than FC (such as NFS or iSCSI) are not currently supported"

because you are using iSCSI storage the only "supported" option you have is "in guest"

[tsquillario]

Did you end up going with the MSCS option with the in-guest MS iSCSI Iniator? I'm just looking at depoying this same setup, wondering how it went?

[KennyView]

Configuration is working fine, just need to take care of arp resolution (http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&docType=kc&docTypeID=DT_KB_1_1&externalId=1006525)

[vGuy]

I am not sure if it's already included in the docs but you should ensure the DRS anti-affinity rules are setup for MSCS VMs which are using in-guest iSCSI Iniator. To ensure both the VMs are not running on the same host at any time.