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Disk Partition Alignment
How much would it be worth to get significant improvement on you Windows Servers for Files, Exchange, or even SQL Server? What if your only investment was time? Well, if the concept of Disk Partition Alignment is new to you, then this tip is made for you.
Microsoft released a white paper on Disk Partition Alignment Best Practices for SQL Server in 2009, providing guidance for aligning your disk partitions according to the disk usage. They claim that in some tests, performance for disk intensive systems have increased up to 30%. That some pretty awesome improvement for something that costs nothing more than time.
I have known for years that creating a cluster size of 64k when formatting a disk supporting SQL Server increases database performance. The reason this is true is because SQL Server readsor writes 1 extent each time it hits the disk. An extent consists of 8 pages, which in SQL Server is 64k. So, aligning your partition size with the database software synchronizes both so neither the disk subsystem or the database engine are waiting for the other to complete their task.
Disk Partition Alignment takes this one step further. Disk Partition Alignment causes the physical disk access to align with the operating system disk requests. If the disk partition is off partially from the physical location when the disk is accessed, it requires two operations instead of one, when the access crosses a hardware boundary.
Depending on your disk access for tools other than SQL Server, you may find improvement as well. Exchange was noted to have a significant boost.
Here’s the bad news…in order to change your partition alignment, you have to create a new partition on the disk. You can’t change the partition alignment without data loss. This can be a time intensive task that most likely will have to be done off hours. You’ll probably create a whole new partition and move existing data files to the new partition, allowing the old partition to be re-provisioned.
There are tools in Windows Server 2008 that make this alignment task much easier, in fact, alignment is the default configuration. The white paper provides specific instructions for each version of Windows Server and how/if alignment is required.
I found it interesting that alignment had benefit on SAN drives as well as direct attached drives. So, even those of us with SANs may need to take a look at these best practices.
Send me a note about your experience if you chose to align your partitions. You can even send other optimization tips you’d like to share with our readers. Reach me at btaylor@sswug.org.
Cheers,
Ben
$$SWYNK$$
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