Virtualization Successes and Your Shop

We disassembled our SQL server cluster in favor of a virtual environment because new technologies like “server snapshots”, and VMotion” make failover and disaster recovery so much more robust than clustering. It also allowed us to cut back on licensing by using the “Standard” rather than the more expensive “Enterprise” version of SQL Server. We have rarely had performance issues due to our servers running in VMWare and when we did we were able to fix it by adding memory, processors or by moving it to faster storage. All of which would have required a major outage if the servers were physical. In the 3 years or so that I have been moving my servers to VMWare I have had 1 short outage where the VMWare host went down and the servers were automatically “VMotioned” to another host and restarted. Total outage was approximately 1 minute. In another case a storage subsystem went down and all data was lost. We restored the most recent server snapshots and then restored the appropriate database and transaction log backups. We were down approximately 3 hours and lost about 15 minutes of data. Compare this to recreating a cluster or even a single server and restoring all the data and the recovery time pales in comparison.

Virtual environments also allow for hardware upgrades much easier than with physical. To move a SQL Server to a new physical box I would have to load an operating system and all the corporate amenities (anti-virus etc.), create a new server name, and IP address. Load SQL Server and move all my data to the new server. I would then need to point all my clients to the new address unless I have DNS aliasing set up. This process could take as long as a week with time on site in the evening to move data when users are in bed. In contrast, a new Virtual Host is purchased, ESX software is loaded, it’s joined to the VMWare cluster, servers are migrated off the old host and the old host is shutdown and retired. No down time, no interruption in service and much less time spent in installation and configuration.

In my opinion, the key to a successful deployment of SQL Server in a VMWare environment rests solely on the availability of talented resources to maintain the infrastructure. Our deployment, though very robust, is also extremely complicated. We have technicians responsible for storage subsystems, fiberchannel switches, enterprise backup systems, blade centers etc. Much of which would not be necessary in a “physical server” environment but are essential in a “virtual server” environment. Every area of expertise is overseen by a technician that specializes in that area but also crosstrains in other disciplines. This is not the environment for a “mom and pop” shop or those faint of heart.