topic Re: Controller Failure - P2000 G3 in MSA Storage

Controller Failure - P2000 G3

WarNox — Thu, 22 Oct 2015 11:54:10 GMT

Hi,

If a volume is only mapped to all ports on it's owning controller, and that controller fails, will a rescan of storage adapters be required in vSphere in order for ESXi to pick up the volume on the surviving controller?

Thanks,

Greg

Re: Controller Failure - P2000 G3

Torsten. — Thu, 22 Oct 2015 12:00:59 GMT

If a volume is only mapped to a single controller, the other controller will not present it.

Why not map the volume to the other controller too?

Re: Controller Failure - P2000 G3

WarNox — Thu, 22 Oct 2015 12:25:05 GMT

According to, http://www.hp.com/hpinfo/newsroom/press_kits/2010/JustRightITopk/MSA2000_G1_White_Paper.pdf (page 11-13), the other controller should present the volume if the owning controller fails?

And according to, http://h20195.www2.hp.com/v2/getpdf.aspx/4aa3-2141enw.pdf (page 16), a volume should be mapped to all ports on the owning controller?

I might have mis-understood something though.

Re: Controller Failure - P2000 G3

Torsten. — Thu, 22 Oct 2015 12:40:21 GMT

From P2000 SMU guide:

To maximize performance, map a volume to at least one host port on the controller that owns it. To sustain I/O in the event of controller failure, map to at least one host port on each controller.

The server will detect multipathing and will work with the owning controller only until this controller fails (it is ALUA).

Sorry, cannot open your links.

Re: Controller Failure - P2000 G3

WarNox — Thu, 22 Oct 2015 13:01:04 GMT

The second link is the Technical White Paper for the HP P2000 G3 MSA and it states.

Volume mapping

It is a best practice to map volumes to the preferred path. The preferred path is both ports on the controller that owns the Vdisk.
If a controller fails, the surviving controller will report it is now the preferred path for all Vdisks. When the failed controller is back online, the Vdisks and preferred paths switch back.

Best Practice

For fault tolerance, HP recommends mapping the volumes to all available ports on the controller.

For performance, HP recommends mapping the volumes to the ports on the controller that owns the Vdisk. Mapping to the non-preferred path results in a slight performance degradation.

Suppose that isn't 100% clear but the SMU does have that one sentence as you pointed out.

Alright I'll have to modifying the mapping. I suppose modifying the mapping while IO is in progress isn't recommended? Even though it's only adding in the non-preferred paths.

Re: Controller Failure - P2000 G3

Torsten. — Thu, 22 Oct 2015 14:16:08 GMT

This manual is trying to cover G1 to G3, but AFAIR it was a bit different with G1.

I would map both controllers, this can be changed (adding ports) online.

Re: Controller Failure - P2000 G3

WarNox — Thu, 22 Oct 2015 14:29:07 GMT

Cool, I'll map both controllers.

Just to confirm, as I can't find it explicitly written in the SMU, I can select the two ports on controller B in the screenshot and click apply without hosts losing access to the LUN?

Appreciate all the help!

Re: Controller Failure - P2000 G3

WarNox — Thu, 29 Oct 2015 22:25:37 GMT

Thanks Torsten, appreciate all the help. Adding ports online worked without a glitch.