Database Reference
In-Depth Information
to meet this expectation.
The bottom line: Given the critical nature of the medical devices it monitors and
subsequent database requirements, the company never should have been using a single
instance of the SQL Server database sitting on a lone physical server. There was no
inherent high availability capabilities built in to this infrastructure. There were too many
single points of failure present in the current infrastructure. It was just a matter of time
before the database went down and stayed down for a long time.
A virtualized infrastructure by its very nature provides a very redundant, highly
available platform to run a database on, thus allowing the DBA to meet very robust
service levels. In this example, the company would have been better able to meet the
implied SLA of little or no downtime had the database been virtualized. When it was
determined the BIOS setting on the physical server would have to be changed, the
company could have simply used vMotion, a feature of VMware, to move the SQL
Server database onto another server, without shutting it down, and then move it back
onto the original server once the BIOS change had been made.
Avoiding the Good Intention BIOS Setting
You might be curious what the BIOS setting was that so negatively affected the
performance of the SQL server database mentioned previously—and, more importantly,
whether you have it set incorrectly within your own environment.
One of the first things experience has taught me to check is the power management
settings for any server a database may be placed on. The default BIOS setting for a lot
of servers is a “green” friendly setting. The intention of this setting is for the server to
save energy when it becomes inactive and then for the server to restore itself as quickly
as possible back to a fully operational mode when activity is again detected. That was
the idea in theory; in practice, many times the server does not ramp up the CPU quickly
and in some cases never allows the CPU to reach its maximum speed.
Another BIOS setting to be aware of is called “dozing.” Dozing slows down the CPU
only, to about half its speed. The good news is it does save energy; the bad news is it
slows down the CPU to half its speed. The proper setting for any server hosting a
database is “High Performance” or an equivalent setting, even though this most likely
means higher energy consumption.
Here are some other settings in the BIOS you should look for:
Enable Turbo Mode in the BIOS if your processors support it.
Enable hyper-threading in the BIOS for processors that support it.
Enable all hardware-assisted virtualization features in the BIOS.
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