Data Backup and Recovery

LUN alignment Windows 2003 cluster


I have a Microsoft Windows 2003 SQL cluster which was deployed on a netapp 6040. We have Data ONTAP 7.3.3.

Windows 2003 cluster’s only support basic MBR disks without third party add-on like Veritas Storage foundation.

When this Windows 2003 cluster was setup the Netapp LUN was formatted in Windows-GPT. In Windows 2003 the format is configured as Windows Basic Disk (MBR). My question is what is the ramification of this? Will this cause a LUN misalignment?

When I run “wmic partition get BlockSize, StartingOffset, Name, Index”

The shared storage disks report 32,256 startingoffset This appearts to report that the LUN is properly aligned.

Am I missing something here?

keep in mind that I have read through this



I could be wrong but it was my understanding that the LUN type specified when creating a LUN was used to accommodate for the fact that different partition table types start the first partition at a particular offset. I think ONTAP aligns the LUN correctly according to the LUN type so that you don't need to be concerned about alignment.

However, if the partition table on the LUN is not the same as it was configured/formatted for, chances are the LUN is not properly aligned on disk. The ramifications are that in the worst case the filer is having to fetch two disk blocks for a single file system block requested, thus using more IOPS than necessary. This usually manifests itself greater on file systems with random reads rather than sequential reads.

Personally I would recommend that you create a new LUN with the correct type and migrate your data from the old to the new.




Using a LUN of type "windows_gpt" to host a Windows MBR partition will cause block alignment issues.

The following KB article has some good details.