Running large SQL VMs on ESXi

[Gabrie1]

Hi

When deciding to run or not to run large SQL VMs on ESXi, what are the points you take into consideration?

- How much more physical RAM should the ESXi host at least have compared to the VM? If I have a 96GB VM on a 144GB host, would you use that room for other VMs as well? Would you go for even bigger hosts? Or would you make this a one-VM-host?

- In a "one VM per host" scenario, are there still enough reasons to virtualize the VM? Is VMotion, portability of the VM, easy adding disks, resizing disks, resizing memory still enough reason to virtualize this VM?

- When I now add Microsoft clustering into the equation, killing VMotion and some flexibility, is it still feasible to virtualize this SQL Server?

I do know about how capable ESXi is of running this workload. I do have the performance white papers on HOW to virtualize SQL successfully. My question mostly is on: Should you...

Gabrie

[JLackman · Accepted solution]

This is like arguing about politics; there will be folks with all kinds of views and much of it comes down to personal views. Some things to consider;

1) you don't mention how CRITICAL (averse to downtime) the database is. If it is super critical you are certainly looking at HA or even Fault Tolerance. This increases the resource requirements considerably on a VM.

2) even if you use a "one vm per host" approach, you need to ensure that you have that availability on OTHER hosts in case HA is triggered.  So essentially you would need two hosts per VM

3) considering the above, and how this escalates as you get into redundancy, HA and FT, you would want to cost compare a clustered hardware HA environment.

Personally, we faced this in a prior job. We went with hardware clustered physical servers.  In my view, if the server is simply large, but doesn't need HA or FT, then I'd consider virtualizing it. If it requires those features, the supporting hardware costs escalate considerably. Size alone isn't a huge problem assuming you have the SAN space or storage. I'm currently supporting environments that have VMs that are over 1 Tb and run fine.

Hope this helps.

[Josh26]

Hi,

As above, if it was me, it wouldn't be about "one host", but multiple, with HA.

From there, I wouldn't have any concern putting extra VMs on that host, but I'd probably avoid a second busy SQL server. I'm sure you have some low user servers you could consolidate with this high use one.

[jrmunday]

Given the Microsoft licencing model for SQL server the "should you" question is an easy yes as virtualising them can provide huge annual savings. There are also all the added benefits that virtualisation offers over physical hardware, so I would avoid MS failover clustering if possible.

Memory is relatively cheap and I would focus on understanding the IO requirements to determine if you can satisfy them on your storage infrastructure. Taking a holistic view of the requirements, what works best from a technical and operational perspective? I would try and consolidate as much as possible (with HA, DRS) provided that the application requirements are met appropriately.

I am currenly deploying new ESXi 5.0 clusters to try and virtualise SQL 100% (if possible).

Cheers,

Jon

[Gabrie1]

Thank you all for the replies.