We're undergoing an enterprise consolidation and virtualisation project at the moment, and I currently have an external consultant proposing to replace our physical, clustered SQL Servers, with non-clustered VM's where the high availability is provided by VMWare HA.
Does anyone have a view on this? Any serious pitfalls / constraints to take into consideration?
Thanks in advance.
plusses and minuses
the plus is that the failover is on vmware so if it does failover none of the SQL services stop. apps just won't be able to connect until it fails over to another node, but all the spid's will still be there. you can also ship the complete VM with all databases to a DR site and just mount it on another VMware node
another plus is that windows clusters are a pain in the *** and changing minor things like IP's can break them. no need for clusters on vmware
upgrading to new hardware is easier. you buy the new hardware and move the VM. no need to reinstall windows
the minus is that the I/O is still limited even if you dedicate drives to each SQL instance. if you have large databases with heavy I/O then you will have problems running them on one vmware node. all the I/O will go through the hypervisor
the db backups might also be a bit slow and you may have to switch to backing up the VM with a vmware aware backup solution like netbackup
the hardware issue can also be a minus. if you have a few SQL instances on a vmware box and you need resources that you don't have you will have to justify a purchase of an expensive server. with non-vmware sql you can buy a cheapo server and move a few databases from various servers to free up resources