topic Re: EVA VDISK creation and preferred path options in Disk Enclosures

EVA VDISK creation and preferred path options

David Korsunsky — Tue, 20 Dec 2005 22:37:20 GMT

Hello. I am inquiring about EVA8000 VDISK creation and the various preferred path settings (no preference, failover only, failover and failback) and the considerations around each one. We have two EVA8000's which we are now testing prior to going into production. Many VDISKS will be replicated via CA using DR Groups, some VDISKS will not be replicated. Hosts are Tru64 (Native failover software), Solaris 9 (DMP) and Windows (MPIO). Looking for some additional information.

Thanks,
Dave

Re: EVA VDISK creation and preferred path options

Luk Vandenbussche — Wed, 21 Dec 2005 02:53:30 GMT

Hi Dave,

I have installed several EVA yet.
I always take the option no preference on the EvA.

I balance the load on the servers through securepath or native failover if the os can handle is.

When I use mpio i also take the default option. I never had performance problems

Re: EVA VDISK creation and preferred path options

Ivan Ferreira — Wed, 21 Dec 2005 06:49:25 GMT

The command view User Guide has all information that you need. Basically:

- If the OS uses secure path, like hp-ux, windows, linux, the only supported preferred path option is "failover only"

- If the OS does not requries secure path, like Tru64 or OpenVMS, you can select any failover method (failover only/failover and failback).

- All copy sets in a DR group must have the same preferred path configuration, because all must failover at the same time.

Then, you can use evaperf to verify the controller that servers a particular vdisk, and the controller utilization.

Re: EVA VDISK creation and preferred path options

David Korsunsky — Wed, 21 Dec 2005 10:02:24 GMT

None of my hosts will be using SecurePath on the EVA8000's.

So if I choose no preference, will the controllers load balanace themeselves and make sure any copy sets that are needed for CA are on the proper controller?
If I have several LUN's in a DR Group is there any disadvantage to using no preference as opposed to the other choices?

Re: EVA VDISK creation and preferred path options

Ivan Ferreira — Wed, 21 Dec 2005 10:27:05 GMT

In our experience, setting no preferrece does not balance the VIDSK between the controllers. All units are presented to the first booted controller. So, is better if you set the preferred path manually.

The DR group won't have problems if you configure no preferrence, but you will have better performance if you distribute the load between the controllers.

Re: EVA VDISK creation and preferred path options

David Korsunsky — Wed, 21 Dec 2005 11:04:52 GMT

Has your experience with the no preference settings and load balancing been more on EVA 3K5K or 4K6K8K or both?

Re: EVA VDISK creation and preferred path options

Ivan Ferreira — Wed, 21 Dec 2005 13:05:13 GMT

We use EVA5K, and soon will install EVA4K. All our systems are Tru64 Unix with TruCluster.

Re: EVA VDISK creation and preferred path options

Alzhy — Wed, 21 Dec 2005 14:06:32 GMT

For HP-UX Vdisk clients that will use SecurePath - use Path Preferencing. Divvy up the LUNS accross the controllers/paths...

Re: EVA VDISK creation and preferred path options

David Korsunsky — Wed, 21 Dec 2005 14:26:40 GMT

I guess what I am getting at here is when you have two EVA8000's in a Continuous Access setup with
Tru64
Solaris
Windows
is it best to use "no preference" and let the array manage preferred paths, or is it advisable to plan out which preferred path setting will be used on each LUN.

Re: EVA VDISK creation and preferred path options

Alzhy — Wed, 21 Dec 2005 14:29:55 GMT

In that case, no preferencing since the client OS'es mentioned do have native pathing support as mentioned.

Re: EVA VDISK creation and preferred path options

Ivan Ferreira — Wed, 21 Dec 2005 14:56:46 GMT

If you set to "no preferrece" they won't be fairly balanced. Manually set the preferrence, also, you must know that when you set the preferred path for any member of a DR group, all other vdisks in the same DR group automatically configures the same preferred path, you don't have to do it manually. (I just tested).

Re: EVA VDISK creation and preferred path options

David Korsunsky — Wed, 21 Dec 2005 17:16:03 GMT

Good info, thank you.

Re: EVA VDISK creation and preferred path options

Ivan Ferreira — Thu, 22 Dec 2005 08:08:01 GMT

Dave, take a look to:

http://forums1.itrc.hp.com/service/forums/helptips.do?#33