Dave Lutz wrote a great article about partition alignment. This is an important technique to optimize your storage.
If you create and access logical disks (aka LUNs) from your Sun Unified Storage appliance, whether over iSCSI or FibreChannel, you should be aware that client side partition alignment can have a big impact on performance. This is a generic issue that applies to any virtual disk interface, not just Unified Storage, and relates to how client generated virtual disk I/O maps to actual I/O in the appliance. The good news is that it can be quite easy to properly align partitions.
Aligning application block sizes to file system block sizes is a common technique, but you shouldn't stop there. When you are not aligning the all block sizes to the native structure of your storage system you end up with reading or writing additional data because of the misalignment, thus reducing the performance of your storage unnecessarily.

The reason is obvious. You can't read or write bytes from or to a disk, you can just read and write blocks. It's called block device for a reason. When a file system block aligns to the native storage block you have to read just this block. If it's not aligned, you have to read the block with the first half and the block with the second half, thus you've doubled the reads.

It's really easy to prevent such an behaviour, and Dave's article explains the necessary steps to do so. Really worth a read.

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