Ok, I have a question. I see Joe and Linchi going back and forth abotu disk alignment and RAID. Yes they are two different things, and something about not needing to align the disks on RAID 1? Or if you are writing to a single drive? I am lost. The article is great, I just want to understand better. Here is the questions I posed on another forum, and have yet to get an answer..
I recently read some information regarding aligning the Disk for use with SQL Server. Meaning, since SQL Server handles data in chunks of 64KB that the disk drive SQL Server writes to should be configured to work in 64KB chunks. The articles I am referring to are listed below, and I am wondering what other peoples thoughts are. I am also interested in understanding how to determine whether my disks are aligned and/or how to align them. Based on the articles, I see my Offset is 32KB on my drives, but I am also trying to work
with the formula in the Microsoft KB article to determine how/where exactly I become aligned. The formula is:
((Partition offset) * (Disk sector size)) / (Stripe unit size)
Questions:
1. Does SQL Server read/write data to disk in 64KB (Extent)? Or is it 8KB (Page) Level?
2. Where do I find the values listed in the formula above? I am a little confused how they got the values to determine where the alignment occurred.
3. Do you only do the alignment on drives where SQL Server is writing data/log files?
4. Does setting your offset to 64KB affect the way the OS stores data on the drives? Meaning, a 65KB file will actually use 128KB? And in that case the remaining 63KB is wasted?
The articles I am referencing are listed below.
http://support.microsoft.com/kb/929491
Based on this article, I have these questions:
1. Does this only matter on RAID volumes? Or, assuming I am only writing to a single disk, should I bother aligning??
2. Can you align the C:\ drive in a similar way?
3. Do all the OS's 2000, 2003 and 2008 allocate the 63 sectors??? for its own use?
Thanks in advance for your help.
John
john.m.couch@gmail.com