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jshaw08

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Replacing SAN LUN Disks on a SQL 2000 Cluster

We currently have several Microsoft 2000 SQL Servers running on Windows 2003 clusters, both A/A and A/P connected to a Dell EMC CX3-20 SAN. To improve performance we are completely re-carving our SAN to up spindle counts. We plan to keep all drive letters the same so SQL doesn't freak out.

The steps we intend to take are as follows:

1. Shutdown the SQL instances
2. Backup all data raw
3. Delete all of the Disk resources for each instance
4. Re-carve everything on our SAN with the exception of the Quorum disks (so the Windows cluster doesn't have to be taken offline)
5. Re-add the disk resources using the re-created LUN's and assign the same drive letter to the disks holding the same data
6. Restore the raw data to all of the respective disks
7. Start the instances

Am I completely mad? Anyone see an issue with this?

If we did have to re-create the Quorum disks what additional steps would be needed?
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David
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Upping spindle counts won't necessarily improve performance, other things can be done when reprovisioning the storage.  Make darned sure you know how the EMC is physically carving up the data and get it to match.  I.e, if the EMC is using an internal disk block size of 128KB, and it is arranged as RAID1 then whenever you write even just 1 byte, it is forced to write 256KB.  If you are using other RAID levels, then you could very well see a write translate to 1MB or more.

So rule #1 - Figure out optimal RAID block size and configure the SQL to match.  
Rule #2, SQL server natively reads/writes in chunks of 64KB.  Make the RAID match this if you can.
#3 - Create proper file system chunk/allocation sizes, and set up to align I/O.  Great time to do this, since you are going to a backup anyway.  You could easily squeeze another 25-50% performance just by doing this and changing nothing else.

Read this whitepaper about alignment for NTFS/SQL server. It is written with Win2K8 in mind, but everything is still valid for other flavors of SQL server/Windows
http://msdn.microsoft.com/en-us/library/dd758814.aspx
(Note if you are using virtualized machines, then all the rules change, because you have to factor in I/O characteristics of your hypervisor)
In a short answer, yes you are.
Do you have SAN copy options? Do you have the space to create the new LUNS without deleting the old ones? i.e. SAN copy current LUN data to new LUN location?
Did you check with Dell/EMC on what solution/steps they would suggest (presuming you have the support)


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jshaw08

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Dell/EMC is working out the architecture, I am not concerned with this. We have about 20TB worth of storage and it's near full, we cannot do a SAN copy. I am only concerned with trying to avoid reloading servers/SQL and save  some time. We are just going to setup a lab and test it out. If anyone has any experience moving LUN's around in a SQL 2000 A/A Clustered environment I would love to hear your input.
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r_panos

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