LUNs and Storage Partitions

[SRENMAN]

When using the IBM DS4700 SAN and if ESX only supports one active path to a LUN at a time - If I have one LUN for Production and another LUN for Test, would I be better off creating a storage partion for each and then having SAN CTRL A -> preferred path to Production LUN and SAN CTRL B -> preferred path to Test LUN? the attached picture shows how I have two paths from each HBA to FC switch and SAN. I would like to optimize traffice as much as possible. Any suggestions?

Thanks

[MattG]

I would recommend creating seperate LUNS for Prod vs Dev/Test data. Having both types of data on the same LUN could cause perf issues or more imporantly could cause the LUN to run out of space (with snapshots). The other benefit of seperating these LUNs is that you could create a lower perf RAID or disk type for the DEV/Test LUN to save on resources.

As for the paths, is this a FC or iSCSI SAN? If it is FC, youy would be hard pressed to saturate the path to the point where you would want to manually set paths, but always "it depends" on your environment.

-MattG

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[SRENMAN]

So I have Separate LUNS, PRD is Raid 6p+q, TEST/DEV is RAID 5. This is a 4G Fiber channel fabric, WIth The IBM DS4700, I believe I have no choice in the matter and have to create storage partitions to these LUN's.

Am I correct in assuming that I would be better off for performance to have each LUN on a separte storage partition and each Controller being the preferred path to the physical SAN disk? I'm licensed for up to 8 Storage Parts and only have 2 LUNs now.

Thanks,

[AndreTheGiant · Accepted solution]

Am I correct in assuming that I would be better off for performance to have each LUN on a separte storage partition and each Controller

Absolutely.

For each RAID group (or group of physical disks), 1 single LUN.

At least 2 LUN.

If possible (if you have 4 path and lot of disks) consider also to use 4 LUNs.

Rember each LUN must be < 2TB.

Andre

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[MattG]

From looking at a description of IBMs storage partitions, they appear to be a licensed restriction to how many hosts can attach to the DS4700? If so, then both of these LUNs would be accessed from the same hosts, so it should not take up another license?

Having the LUNS on seperate raid groups will normally give you better performance as the dev/test LUN will not compete with the disks on the prod LUN. In theory using seperate paths will give you the best performance. But you normally would be hard pressed to tax a 4GB FC connection with only 2 LUNS. Many VM admins are running hosts with 20-30VMs across 10 LUNs from the same hosts without worrying about the paths. In the case of active/passive arrays this is not even an option.

-MattG

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