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June 18, 2010


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Chad, fyi I commented Aaron's post w/ my 2 cents about linux part alignment (64k/emc case), for kickstarted installations, + the gparted tip you suggested.

Aaron Delp

Thanks for all the follow up! Great information!

John F.

Hi Chad,

In Windows 7/Windows 2008, a 100MB system reserve partition is created on the first drive, and then the "first partition" begins at the next 1M boundary. For other drives, it depends on the drive type. GPT partitions are aligned by default.

Yes, under the covers NetApp (I work for NetApp; for more info check the link on my name) has a granularity of 4K. As long as you align on a 4k boundary, that works. 64K (which is a multiple of 4K) works fine.

If you use snapdrive to create LUN on NetApp, alignment is taken care of for you regardless. If not, you could potentially have issues. Just in case, I wrote a very short PowerShell script which runs on Windows and is storage vendor agnostic so that folks can check their Disk alignment. Clearly this won't run on Linux, but if you want to check disk alignment of a Windows guest, well have at it. You can find it here: http://communities.netapp.com/docs/DOC-6175




Good post well explained guys, my customers rarely are aware of this and when you start to explain it in it's simplest form as follows, it makes for an even more compelling case:
If the average performance improvement case is 7% which seems small and i have tested this to much higher values, then an unaligned system will equate to a performance loss of 1 disk per enclosure with EMC storage arrays.
i know that has a cleared message to my users, additionally i found that Microsoft had updated their KB in June 2009 to now recommend that Windows platforms all use the 1024 alignment which equates to GPT formatting.
Thanks again guys, keep the knowledge coming



Nick from NetApp...

If you're using gParted, just a head's up that it also has a 1MB partition offset options. This means, with vSphere5, that Microsoft, Linux, and VMware have all standardized on 1MB offsets.

This is good news.

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