Active IQ Unified Manager Discussions

Disk alignment vs NetApp

NETAPPKOSMOZZ
9,871 Views

Hi,

I am looking for the best practices to align disks on a Windows 2003 R2-system with a SQL-server 2005 (virtualised on VMWare).

I am also looking for the stripe unit size, may'be I am to deep into it today that I can't find it right away.

As the underlying offset is 4KB on NetApp (am I right?), and the offset on a disk (located on a LUN) is for example 64KB (=best practice SQL server), is the disk thus mis-aligned or not?

Reporting error from Insight Balance tool: "This LUN's disk partition is not aligned with the underlying storage array. The backing storage for this LUN is a NetApp array which recommends alignment on 4KB boundaries. A misaligned LUN partition may impact performance and cause unnecessary load on the disks."  So we can suppose that this error can result into high latency numbers.  Is there a way I can detect the performance of the misaligned LUN, and afterwards, when realigned, to see an improvement or not... ?

As I can see in the Insight Balance tool, those disks are misaligned.  How does Insight Balance tool measures this state? 

Also, when i look into other LUN's, i can see that the status varies from "aligned" to "misaligned" to "unknown"?

I'll take it a little bit further, when looking at the LUN's, i can see to type of numbers, one that states "Vendor Recommended Alignment: 8/4" and one that states (for example) "Alignment Offset (blks/KB) 6/3".  How do I need to understand that?

What is than the best practice to modify it?

If you look at the Avg. Response time of those misaligned LUN's, some are quite high.  These response times are added to the response time of the host, in this case Windows 2003 R2 and SQL-server.  So a read/write latency of more than 40ms, is not absurd in the case of misaligned LUN's...?

Thanks for your input!

An enthousiastic, new NetApp partner,

Filip

13 REPLIES 13
Public