MBRAlign - Offset and Alignment. Are both these handled by MBRAlign?

[stuarty1874]

I have attached a screenshot of a VMDK that I have aligned using MBRalign.  It shows the disk as aligned but the offset is still incorrect.

I’m getting a little confused and was hoping someone can push me in the right direction.

Can someone tell me if the MBRalign Tool takes care of both alignment and offset remediation?

[RAFAEL_GUEDES]

Hi,

The offset is ok, because this is divisible by 8. Since WAFL logical block size is 4KB and disk sector is 512bytes, this results in 8 disk sectors.

If you have any doubts, refer to TR-3747.

[stuarty1874]

Thanks Rafael. I reviewed the document again last night.

We have several virtual machines that have an offset of 65536.  This also devides by 8.  Does this mean that these disks are correctly aligned?  If that is the case what should we be aiming for as a standard?  Should we look for an offset of 32768 or 65536?

[stuarty1874]

Just found this thread...

http://communities.netapp.com/thread/3954

[jeremypage]

Either is fine. The goal is to be able to break cleanly along 4k block lines (4096). So there are multiple offsets that will get you aligned. Newer OSes will do this for you (2008R2 for sure, new Linux versions as well).

if MBRAlign says you are good you are. Really all it's doing is checking your offset and if it's not divisible prepending free space and dd'ing the rest of the file to the end of it so it is.