SQL server physical vs virtual

[Nikhil_Patwa]

Hello,

Wanted to know what are the best practises of SQL Server for large ERP implementations having 300-400 users, would like to know if we can use virtualized SQL Server 2008 hosted in ESXi 4.1 for such an implementation or should we have a physical SQL server, what are the pros and cons and would be glad if there are any benchmarks of SQL Server providing comparisions between physical and virtual that would assist in making correct decision.

Most of our servers in the ERP implementations will be virtual - AD, Application servers, file servers, web servers etc.

I read an article where it descibed the performance of virtual server running in ESXi compared to physical and it said the performance of a VM is

80% of a physical server, am not sure whether its true.

I have been virtualizing servers for some time now and our datacenter is fully virtualized with many ESXi servers, vCenter Server but our userbase is not so great compared to the ERP solution we are going to implement for our client and thus wanted some guidelines.

Hoping to receive some good feedbacks that will assist in my decision making.

Nikhil

[ChrisDearden]

As long as you take some care when deploying the SQL box and your underlying virtual infrastructure is sound, then I see no reason why you can't deploy it as a VM. a 20% performance overhead sounds a bit much - have you a link to where you read that ? What spec physical server would you deploy for this ?

[Dave_Mishchenko]

Here's a good document to look through regarding SQL scalability - http://www.vmware.com/files/pdf/perf_vsphere_sql_scalability.pdf.  The overhead comparing physical to virtual runs between 8% (2 vCPUs) and 14% (vCPUs).

For the size of server you'd be looking at you'll be fine with CPU / memory on vSphere.   I would pay particular attention to your storage configuration for the SQL VM.

[Nikhil_Patwa]

The physical hardware for Database server would be 4 x 6 core CPU, 64GB RAM, 6 x 146GB (15k RPM) hard drives in RAID10 preferably, there's also a SAN where all the VMs and DBs resides - now to go for virtualization or install SQL server on the physical server is the question.

In terms of hardware sizing its pretty much powerful and we also thinking of using the same speced hardware for ESXi hosts with double the RAM capacity (128GB)

Nikhil

[ChrisDearden]

Thats a preety beefy SQL server - but have you any current baselines of acrualt utilisation ?

SQL will eat all the RAM you can throw at it - the more RAM you use , the less disk you need.

consider the usual seperate volumes for Db/Logs/tempdb - make sure you use the pvSCSI controllers on those additional volumes for an extra boost.

[Tanav]

you can easily create SQL Virtual Cluster. i have recently create SQL virtual cluster where is underlying hardware is IBM having 256 GB RAM on each server and backend storage is Netapp. Apart from that i have created another 30 VMs which are running on the same servers.

thanks

Dhiraj

[Dave_Mishchenko]

Depending on your vSphere licensing level the SQL VM would be limited to either 4 or 8 vCPUs.  Does the spec for a physical host really call for that many physical cores?

Memory will be no issue as you can go with up to 255 GB per VM.  When you're looking at the storage design you'll just want to ensure that the underlying storage can provide sufficient I/Os to serve the users adequately.  Whatever you spec out with a physical server I would ensure that you spec the same for a VM and ensure that your storage system will gaurantee a specific I/O level to the VM (or physical box).

[macpiano]

I just attended the VMUG user group conference and this was one of the topics. Considering everything equal your performance will be pretty close with virtual. The biggest difference is that if it is virtual you have the capabiity to move it if need be while it is on. The presenter's tests showed with a heavy duty Oracle database that there was little difference even in heavy iops. 

[Nikhil_Patwa]

Hello,

We have thought and also tried some comparisions, finally we agreed on the VM path for SQL server.

Nikhil