Importance of disk alignment


For those who took the habit to align their storage partitions in Windows 2003, you will happy to know that Windows 2008 does it automatically and for the boot disk as well !

 

By default Microsoft uses an offset of 1024KB (2048 sectors) to cover most of the stripe unit size scenarios.

For example our EMC storage uses 960KB but most of the storage vendors use 32KB or 64KB for their stripe unit size.

 

To align a partition with Windows 2003 you have to use the DISKPART utility (not DISKPAR) along with the create partition primary align=1024

But unfortunately you cannot do that against the C: drive obviously (although there are workarounds out there…).

 

VMware aligns as well its VMFS partition when you create them from the VC client only! The offset is 64KB (128 sectors).

 

To verify your offset in Windows use this command: wmic partition get BlockSize, StartingOffset, Name, Index

 

Here is a little diagram showing the boundaries crossing:

 

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About PiroNet

Didier Pironet is an independent blogger and freelancer with +15 years of IT industry experience. Didier is also a former VMware inc. employee where he specialised in Datacenter and Cloud Infrastructure products as well as Infrastructure, Operations and IT Business Management products. Didier is passionate about technologies and he is found to be a creative and a visionary thinker, expressing with passion and excitement, hopefully inspiring and enrolling people to innovation and change.
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One Response to Importance of disk alignment

  1. Pingback: iSCSI Tweaks and Recommendations « DeinosCloud

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