Posted by: Nathan Simon
when relevant content is
added and updated.
If you are working with VMware of Hyper-V then you know what the heck I am talking about. Aligning the OS’ data blocks with the SAN.
There are many ways to do this, but a lot of people are unaware of easy ways to do so.
Some people know of the WMIC command, and some people know of Sysinternals DiskEXT. So how do you use these tools? Well let me show you.
type this at the command prompt : wmic partition get BlockSize, StartingOffset, Name, Index
You will get the following output:
BlockSize Index Name StartingOffset
512 0 Disk #1, Partition #0 1048576
512 0 Disk #2, Partition #0 1048576
512 0 Disk #0, Partition #0 1505755136
So what do those numbers mean to you? well as long as the StartingOffset (1048576 or 1505755136 in this example) are divisible by 4096 you are aligned with your storage.
Sysinternals is a little bit of the same, use this is WMIC gives you an error message.
Disk Extent Dumper v1.1
Copyright (C) 2001-2007 Mark Russinovich
Sysinternals – www.sysinternals.com
Mounted at: <unmounted>
Mounted at: D:\
Mounted at: X:\
Mounted at: C:\
As you can see, the disk are all aligned to the SAN.
If you are in a VMware specific environment and have miss-aligned VMs, the easiest way to re-align VMs is to V2V them. VMware Converter 5.x can create an optimized partition layout, if you are looking at cold cloning and hoping it will align blocks, it won’t. You need to warm clone the server. Believe in the software though, it works! Block level replication baby!
Oh and don’t forget to disable SSL encryption to increase your transfer rates by 150%! Go here to find out.