XP512 - Command Device creation

[Ian Dennison_1]

The documentation for performance Advisor for XP512 recommends that if I create a Command Device from an existing LUN, that I be on Offline mode.

Does that mean if I create a CU:LDEV of 50 MB using VSC then assign it to a Command Device, then I do not require the XP Array or the Server concerned to be in Offline Mode?

Thanks, ian Dennison

[Vincent Fleming · Accepted solution]

You are correct. If you are converting an existing LUN to a command device, you should be in offline mode, but if you use a new/unused LDEV and create a new LUN you can do it in online mode.

Good luck!

[Ian Dennison_1]

Thanks Vincent, will charge on with it!

Message closed, Thanks Ian

[Antoni Jude]

I am new to the forum but old to the product.

Just remember that when you add a NEW command device/or change an existing LDEV to command device, it will also take the port offline but for few seconds only (in both online and offline mode of lun management). Hosts connected to the port may time out. We have faced this problem.

The best practice is to map the new command device to one unused/not live/development port first, complete the configuration and then assign additional paths to the command device via which the production servers can see the command device. This way we are only assigning another path to existing command device (can be done online/offline) but not changing the command device mode.

In case a host has two HBA (with high availability software installed), create the command device on the first port where first HBA connected, complete the lun configuration and then assign another path to the same command device using second port where second HBA is connected.