May 27, 2008 at 9:13 am
I have budget to get a standby server that will be located at a 3rd party site away our various SQL servers. I plan to use a mixture of log shipping and database mirroring to this server. I am in the early stages or establishing the pro's and con's of either having;
Physical Server with 1 Operating System and multiple SQL2000/SQL2005 instances.
Physical Server with VMWare installed and multiple virtual servers with a SQL server instance being installed on virtual server.
I am sure others have probably been faced with this task and would welcome any feedback, ideas etc.
Many Thanks in advance.
May 27, 2008 at 10:29 am
I'm confused. Are you getting one warm standby for multiple primaries?
I like VMWare, but keep in mind you'd take a decent sized IO hit here as well as resource loss. If you have this server way overpowered for one instance, I'd actually go the VMWare route, especially as it would be easier to move these virtuals to multiple standbys later.
Instances work ok, though you might need to keep the memory usage low on all but the one that's failed over.
May 27, 2008 at 2:37 pm
I agree with Steve, if you run all of the machines on VMWare, you will take a performance hit, but you are only likely to have a single failure at any given time so you could rather easily adjust the resources given to the machine that has failed during a crisis.
This will also make failover much easier as you can easily reassign IP addresses and rename servers to fill the gap of your production server without doing anything at the client. You could do this with multiple instances and DNS, but it would be more complicated.
Watch the support of VMWare and SQL Server - it is only partially supported by Microsoft and only with the retail versions of VMWare (the "free" version of VMWare that runs on top of a windows OS has issues with SQL Server).
May 27, 2008 at 3:28 pm
Thanks for comments so far. Just to clarify, I have around 40-50 databases spread accross different SQL2000/2005 instances. All these instances currently run on HP Blade servers attached to a SAN, there is a couple of SQL2005 clusters for the mission critical databases. So the main reason for this standby server at a different physical location is probably more to cater for the complete loss of the SAN at the data-centre or one of the non-clustered server blades going bang. So I plan to mirror/log-ship some of the databases to avoid any loss of data and to bring on-line for users to access (an automated failover is not totally essential as some of the various applications will need services restarting/re-configuring etc).
We are only using VMWARE for test/dev environments at the moment and works very well. I'm just trying to establish if the Standby Server which will probably be a Dual QUAD Processor and lots of RAM, with RAID 5 and RAID 1 disks needs to be virtualised or not. Or if just running one Physical OS with 1 instance of SQL2000 and 2 x SQL2005 instances will work just as well.
There is probably no right or wrong answer and may depend on various other factors.
Any other comments greatly appreciated.
Thanks
May 27, 2008 at 4:24 pm
So are you trying to back up 40-50 databases to one server? The rules for the standby server are the same as for production, allowing for some amount of slowness because of issues. If you don't want 40-50 instances on one server, then you probably should rethink this.
May 27, 2008 at 9:41 pm
One of the recommendations by Microsoft is that a maximum of 5 databases should be mirrored per server. I think that will rule out mirroring since you have around 10 time that number.
May 28, 2008 at 5:27 am
So you are either talking about 1 instance of SQL 2000 and 2 instances of SQL 2005 on a single server, or three virtual servers.
If you have three servers in production (which I think is what you have described), you will probably be better off with three virtual servers rather than a single instance. You will have more overhead with three virtual servers vs. one server with three instances, but the maintenance is going to be easier because you will simply have to mirror your production environment. You can configure your drives to be the same, even using a shared drive for the three virtual machines to act like your SAN drive. When it does come time to handle a failure, switching to a virtual machine will be easier than dealing with multiple instances. This will also allow you to keep the OS's the same on your failover setup as the three production servers may not be on the same service pack or operating system.
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