SAN switch configuration - migration to active/active

[AB2011]

Hi,

we're planning to migrate our SAN environment (MSA 1500 with 2 controllers, 2 switches) from a fail-over active/passive configuration to a performance enhancing active/active configuration. how complex are the changes that have to be made on the san switches (hp storageworks a-series)? can somebody please provide a basic overview?

thanks
alex

[TTr]

Since you mentioned "fail-over active/passive" in your current setup, you should have two physical paths for each LUN in the array going upwards to each san switch and each server HBA with dual logical device paths in the server. In this case I don't think you have to change anything in the SAN switches. All the changes are in the array and the server OS.

[AB2011]

oh really? that would be great, because the only step in this migration proccess that we were struggling with was the changes which have to be made on our switches... all the other things are clear more or less.

ist it possible to guesstimate the performance boost this operation will bring?

thanks for your reply
alex

[TTr]

You did not mention what kind of servers/OS you have and how the LUNS are assigned right now. But in general, you can still get very good performance with active/passive setups if you have half of the LUNs assigned to one server HBA and array controller and the other half of the LUNs assigned to the other server HBA and array controller. The "other" HBA serves as the failover. By doing this you have a manual load balancing setup where the server HBAs are not doing the I/O at 50/50 exactly but it could be very close.

Moving to active/active in this case you will get minimal I/O improvment, I would guess around 5% maybe a little more depending on your LUN activity and how it is separated across each HBA.

On the other extreme if you have all your LUNs assigned to one HBA and one array controller, and the other HBA serves as failover, then you are running at half of the I/O potential. Moving to A/A would double the I/O.

Whatever the case is, check with the array and server vendors for a support mattrix with what you have for an a/a setup and see if they have any specific requirements for the SAN switches.

But in general if you have standard dual paths in the SAN you should be OK.