SQL 2008 cluster on vmware possibility

APPIREDDY used Ask the Experts™
Hi Guys,
We are planning for SQL 2008 cluster solution on microsoft server cluster.my questions are as follows
What we have:(Existing)

SQL 2008 cluster on windows 2008 server cluster using VMWARE ESX 3.5

Does ESX 3.5 supports this? or do we need to buy physical servers? what are the best practices , advantages, disadvantages and your openions are welcomed

Many thanks

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I have no idea if they support SQL 2008, but i do know they support SQL2005 and they also support Windows clustering on ESX 3.5. Also, i don;t seeany tehnical downsides to doing this
That being said :)  I always have a strange feeling when users go virtualize a Microsoft cluster on VMWare, the only reason you would like to have Microsoft cluster (if using active passive off course) is to have High availability, this is something VMware can also offer.. They only reason i can find is that the SQL servers you are buying don;t have that much load on them so it would be a waste of hardware if you didn;t virtualize them.. Also, clustering in SQL means you have to buy Enterprise SQL (at least, that used to be the case, don;t know the 2008 license setup) which is way more expesnive then simply buying SQl standard.. If you are choosing to HA your SQl, i'd say just creata a few virtual SQL servers on your VMware (hell, why not 4 or 5) and load balance between them.. You have HA and multiple servers to use if SQL crashes on 1 machine..

I also know of some isseus with VMWare's VCB on SQL 2005. Because VCB creates an image of the machine and then starts working in a delta until the image is copied to the VCB server. SQL isn;t really happy with this kind of backup method and has a tendancy of crashing (again, this was on SQL 2005)..
Make sure your infra can support the requirements. If it needs it own disks or nic or controllers......

what is the reason you want to cluster, (you can build clusters on esx), i'm no expert in 2008 but it can also build redundant. (in 2005 you can use the principal/mirror configuration)?
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Hi Guys,
thanks for the reply.without using Cluster solution is it possible to achive high availability all time using just ESX and SAN? my doubt is what happens if the Server A(SQL) goes down. i know the database can be on SAN, what about the all the SQL instances, configuration and e.t.c, so that the users will be redirected to another server(which is possible in cluster solution).We have a Callcentre that needs 24/7 no downtime senario. how can i achieve this? can someone explain, to save me a big cost please?

Many thanks
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HA from ESX 3.5 only means that when a server crashes, the vm will be vmotioned and started at an other esx host. You will get downtime. Best option is then to use the builtin functions of sql (in 2005 it is called principal/mirror, but your applciation needs to be able to work with that), or windows clustering. But when using windows clustering and you will get a failover, there will also be a disruption, sometimes applications do not like this. Make sure to check this with the supplier of the application.
O and by the way, if you are using MS clustering on esx, make sure the nodes are not all on the same host (put in rules to prevent this). Because when the hardware goes down, both (or more) nodes will go down if they are on the same system.
Setup for Microsoft Cluster Service  : http://www.vmware.com/pdf/vi3_301_201_mscs.pdf

just my 2 cents, but i'd bet my money more on an ESX environment with SQL servers on it then using Microsoft SQL clustering.. Not only are you able to spread the risk much more using ESX, you should also keep in mind that Microsoft clustering is a very advanced technique and not easy to implement whereas ESX is almost common knowledge... It's failry easy..

Also make sure that, when you do create MS Clustering on VMWAre to make it a "shared" disc for the quorum instead of private (i thought it was caled this :))


the programer has got no idea about the cluster thing. we are in a testing mode, and we want to see what are best possible means, so that when even one server is getting restarted or completely failed, our application get to the databse and pickup upto date information. the application at the movement using a sql database running on SQL2000 box and client are connecting to the database using front end, which then uses a ini file , which directs the application to the database.
Paul SolovyovskySenior IT Advisor
Top Expert 2008

A lot of what you can do depends on your SAN.  If you have iSCSI then you can configure iSCSI initiator from the VM or use Raw Data Mapping to a LUN that will house your quorum.  If you have FC SAN thinks become a little more complicated, you could use an RDM and you would have to make sure that you put a rule in vCenter to keep the two SQL nodes separated.

There is also a new technology out there called NPIV that will map a VM directly to the LUN but it all depends on the SAN HW, etc, take a look at the link for more info


Running a VMWare Cluster is not a good idea for a SQL server since it will reboot the machine on a different host, my recommendation is MS SQL Cluster and use two VMs with a qourum drive or a virtual and a physical node
A good starting point is http://www.microsoft.com/sqlserver/2008/en/us/high-availability.aspx , High AvailabilityAlways On.
This will be a good starting point for your programmer, decide what HA technique from microsoft you want to use, build your hardware beneath. We are using SLQ 2005 mirroring now on physical boxes, but it also could running on ESX. An other good technique is MSCS, you can build it on physical and virtual hardware.
You should know your requirements, for example: If we have a machine which requires 2 cpu's, and our ESX boxes have also 2 cpu's we prefer physical machines.


Thanks for the reply. i have iSCSI SAN and i could either go for SQL Cluster or mirroring? i could say as long as no data loss, i would be fine. so taking that one into consideration, what do you think are the possibilities? SQL cluster means i need to use MSCS and build the SQL cluster (active/passive) on top.Am i correct?If so can i use 2 vm's who's shared disk are mapped to LUN's using iscsi initiator(my doubt here is should i use iSCSI initiator directly on the windows server or using iSCSI initiator on ESX?)are there any documents or how to's available?
Paul SolovyovskySenior IT Advisor
Top Expert 2008

Your idea would work and you may use the iSCSI initiator from the VM itself, we use this method successfully but it obviously depends on the I/O and load.

Hi Reddy,

I've come across this post while searching for more information myself, but I thought I'd pass on what I've learned so far.

To get official support for MSCS clustering from both VMware and Microsoft you will need to deploy a two-node cluster running Windows Server 2008 on ESX 4.0 hosts that aren't in a DRS or HA cluster and are using FC SAN.

Windows Server 2003 is supported by VMware and on a "best effort" basis by Microsoft, but VMware will only provide support if you use a FC SAN.

After seeing all of the caveats that go with MSCS on VMware (read through http://www.vmware.com/pdf/vi3_35/esx_3/vi3_35_25_u1_mscs.pdf and http://www.vmware.com/pdf/vsphere4/r40/vsp_40_mscs.pdf for more information) I'm very much inclined towards mirroring instead.




thanks for the info guys.
i now setup a sql 2008 cluster on 2 physical machines, with windows 2008 enterprise servers. but i would love to test both windows cluster and sql cluster. what should i look for?how do i know the cluster is 100% good in shape. i mean how do i know everything i set up is OK. i could see the disks, services, network status are 'up'. what else i need to makesure? whatelse i need to check before going for production.

Many thanks guys

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