topic Re: snapdrive for windows in VMware Solutions Discussions

snapdrive for windows

slava — Thu, 05 Jun 2025 07:28:28 GMT

Hello all,

Dealing with performance issue at the customer site i found out that LUNs that had been created with SnapDrive (4.2.1 & 5) are misaligned.

The question is why the SnapDrive cretes LUNs that are missaligned?

Re: snapdrive for windows

kvinay — Wed, 06 May 2009 04:56:18 GMT

Could you give some more information here,what exactly do you mean by misalligned??

-Vinay

Re: snapdrive for windows

slava — Wed, 06 May 2009 09:15:48 GMT

Hello,

I am using document from the following link to recognize if there are missaligned I/O on specific LUNs and also if FS on the LUN is alligned correctly:

https://now.netapp.com/Knowledgebase/solutionarea.asp?id=kb36120

Re: snapdrive for windows

watan — Mon, 11 May 2009 22:23:38 GMT

Snapdrive isn't necessarily causing the misaligned luns, its only sending commands to create the lun and manage it after creation. The article you mentioned has the explanation for the reasons why we could have misaligned luns.

Re: snapdrive for windows

tyeoman_swinton — Tue, 12 May 2009 07:13:46 GMT

What platform type was set for the LUNs? eg. vmware for vmfs etc.

Re: snapdrive for windows

slava — Wed, 13 May 2009 10:10:30 GMT

it was set to windows.

Slava Chubar

Professional Services Engineer

NetApp

972.3.9205538 Direct

972.52.3120538 Mobile

slava@netapp.com

www.netapp.com

Re: snapdrive for windows

yountae — Fri, 15 May 2009 16:27:47 GMT

I think I know what you're trying to say.

You created a LUN using SnapDrive for Windows (That's exactly same to create a LUN with host type 'Windows'), and checked the LUN's offset value from msinfo32. And msinfo32 says the offset is 32256.

You need not worry, when you set LUN's host type to 'Windows', WAFL allocated the 31.5KB to the 'special' block, so the NTFS volume started aligned although the msinfo32's offset is 31.5KB.

To make sure if it's aligned, you can check with perfmon Split IO/Sec counter (not sure) or using wafl_susp from Data ONTAP with Advanced privilege.

Thanks

Re: snapdrive for windows

slava — Tue, 19 May 2009 07:26:30 GMT

The main concern there that even that all LUNs supposed to be aligned correctly there are a lot of misaligned IO on them.

Slava Chubar

Professional Services Engineer

NetApp

972.3.9205538 Direct

972.52.3120538 Mobile

slava@netapp.com