Gail wrote:
> 
> Indeed. The problem with multiple SQL instances in VMs is IO. You can 
> allocate CPUs and memory to specific VMs, but there's still a single IO 
> channel, and SQL database tend to be IO bound more often than CPU or 
> memory.

With Xen you can allocate whole disks or RAID-arrays or whatever and 
amount X of RAM to be used straightly by the VM. In my experience the 
lag is mostly unnoticeable (yes, it probably will be more noticeable 
with DB-server, which I'm not running on VMs (well, there are MySQL 
installations on at least 2 VM's, but they're really small DBs), but 
depending on DB-size etc the saved cost of another HW can possibly give 
you even better HW for that one machine to have better IOs for the DB, 
it's not purely black and white).

Then again, MS surely don't want to support Xen, while they're working 
on HyperV - no wonder SQL Server ain't supported on such 
competitor-software ;).

-- 
Eero "Aero" Ahonen
    http://www.zbxt.net
       aer### [at] removethiszbxtnetinvalid

Post a reply to this message