A big thank you goes out to Andy Yun (b|t) for hosting this month’s TSQL2sday party. This month’s topic is Just Say No to Defaults.
I have a Bachelor’s degree in Mathematics with a minor in Computer Science. So when I say I’m a fairly smart person, it’s not bragging, it’s simply the truth. So when people say, “Any monkey can be a SQL Server DBA”, I find it offensive. While that statement may be close to true, it’s not the whole truth. Yes, Microsoft made SQL Server easy to use right out of the box, but if you want SQL Server to run well, you better have one of those really smart monkeys.
I can’t tell you how many times I have been approached by my friends that are developers, DBAs for other RDBMs or SysAdmins and asked to “fix” their SQL Server environment. They are really smart people, but they made the mistake of thinking that they could simply install SQL Server, accepting all the defaults, be off and running and never look back. The biggest complaint I hear from these same people is that “SQL Server is slow”. My response is usually something like, “Hmm, I can’t imagine why that would be”, in my most snicker-y voice.
There are so many things that can be tweaked in SQL Server to improve performance, but there are two things you can change right off the bat that will make a world of difference. They are the defaults for database file location and max memory. In fact, if you don’t change the default location for your database files and the max memory setting, a lot of the other performance tweaks won’t make that big of a difference.
Database File Location
When the SQL Server install runs, it asks where you want to put your database files. The default location is on the same drive where SQL Server is installed, which is typically the same drive as the OS installation. Do NOT accept this default, just say NO! If you have a high volume transactional system, this will cause competition with the OS and guess who loses? You do. You should take this a step further and separate out your data files from your log files. And your tempdb should have a drive all to itself. (Note: When I say drive, I am referring to physically separate disks, not a single disk that has been partitioned into multiple drives. If you’re using a SAN, make sure you coordinate with your SAN administrator to get your drives created from the correct “LUN pools”.)
After SQL Server has been installed, the default max memory setting is to basically allow SQL Server use as much memory as it wants. Sounds like a good idea on the surface, but just say NO! SQL Server is very greedy when it comes to memory, it will take every byte your server has to offer, leaving your OS starved. My general rule of thumb is to allocate ¾ of the total memory to SQL Server, never leaving less than 2GB, but not more than 4GB, for the OS.
These are not the only defaults you should change, but these are two that will get you the most bang for your buck. They are easy to change and the implications/consequences of these changes are easy to understand. If you are a beginner with SQL Server, start with these two things, they will make you look like a very smart monkey.