topic About EVA 5000 with Secure Path in Disk Enclosures

About EVA 5000 with Secure Path

RogerVI — Tue, 08 Feb 2011 19:55:55 GMT

I have one EVA 5000 HSV110 and I have configured the luns using Command View EVA.
All the luns are presented by default, namely preferred path / mode "No preference".

Some of the luns have the managing controller "Controller A" and some the "Controller B".
The critical servers connected to the storage are HP-UX 11i V1 wih the Secure Path 3.0F

The options in the Secure Path are:

Load Balance: On Auto-restore: On Balance Policy: Round Robin
Path Verify: On Verify Interval: 30

In this configuration, there are 4 paths (2 actives and 2 standby as showed in attached document)
My question is:

Is this the optimal configuration ?

The I/O goes only for the active paths for each lun. Is that correct ?
Please, provide any clues according your experience.
Thanks in advance

Re: About EVA 5000 with Secure Path

hvhari — Wed, 09 Feb 2011 03:44:26 GMT

Hi Peter,

Optimal load balancing setting will depend on the actual usage of the LUNs in the system & the path to the controller owning the particular luns.

Depending on the IO load on each LUN, you can use secure path to configure a preferred path to a LUN with other path as standby. While doing this make sure that the preferred path is via the owning controller.

In you current situation, following will be applicable.
from user guide : http://h20000.www2.hp.com/bc/docs/support/SupportManual/c01683918/c01683918.pdf

Impact of load balancing and active paths
Preferred path and selected path are meaningless designations when you enable load balancing.
Load balancing treats all paths equally and directs I/O to all available paths. In other words, load
balancing is a higher priority than preferred or selected paths.
When load balancing is enabled, as a default, the Secure Path for Active-Passive device attempts to
use all the available paths to a LUN in a round-robin fashion.

If load balancing is enabled and you set the path as preferred, the driver marks the path as preferred,
but the path is not used as preferred until the load balancing is turned off.
If load balancing is enabled and you select a path, the system performs the following actions:
â ¢ If the path is on the standby controller, I/O moves to the standby controller and the selected path
is one of the active paths.
â ¢ If the path is on the active controller, the path continues to be used as one of the set of active path

Re: About EVA 5000 with Secure Path

Johan Guldmyr — Wed, 09 Feb 2011 06:22:22 GMT

You could upgrade VCS to 4.x and then all paths would be active (4.x is active/active, 3.x is active/passive). Then you can split the LUN/vdisk ownership between the controllers so that both controllers do the work.

Re: About EVA 5000 with Secure Path

Don Mallory — Wed, 09 Feb 2011 13:33:34 GMT

Upgrading beyond VCS4100 is very recommended, howerver there are a couple of things to consider:

1. The array will have to be re-cabled to support active-active paths. There is documentation for this, but also HP will do it during an upgrade if you have support.

2. SecurePath, supports EITHER Active-Passive (SecurePath), OR Active-Active (AutoPath). It used to be two separate bundles, but HP changed this in around 2005. You will need to uninstall SecurePath for A/P arrays and re-install for A/A arrays (it's a sub-package selection).

3. SecurePath once installed with A/A, just select Round-Robin as your load balancing policy, and you'll find you get the best overall performance.

4. Preferred paths config in CommandView EVA. This is only to support pvlinks. Yes, it does technically have an impact on Secure Path A/P, but it was never truly intended to.

So, yes, you do have an optimal configuration for VCS3.x and no, you don't have an overall optimal config.

Best regards,
Don

Re: About EVA 5000 with Secure Path

Uwe Zessin — Wed, 09 Feb 2011 15:18:47 GMT

Johan,
it has always been possible to split vdisks across both controllers. This is not a new feature with active/active.
Even the old HSG controllers could do that in 1999.

Re: About EVA 5000 with Secure Path

Johan Guldmyr — Wed, 09 Feb 2011 15:23:59 GMT

Uwe, but if it's active/passive - doesn't that mean one controller is not actually owning any vdisks - is passive(in standby mode?). So splitting it does not make a difference?

Re: About EVA 5000 with Secure Path

Uwe Zessin — Wed, 09 Feb 2011 15:34:59 GMT

There are multiple definitions of active passive. Again, on the EVA, you have always been able to assign different vdisks to different controllers. You just could not do I/O via the non-owning controller.

This is different from the A/P firmware on the MSA1000, were all logical disks were owned by one controller at a time.

Re: About EVA 5000 with Secure Path

Johan Guldmyr — Wed, 09 Feb 2011 16:12:15 GMT

Ah, thanks for clarifying that :)

Peternt: Sorry for hi-jacking the thread a little bit.

Re: About EVA 5000 with Secure Path

RogerVI — Wed, 09 Feb 2011 16:34:51 GMT

Uwe, that means that I could change the ownership of the luns, for example, in Command View EVA (preferred path/mode):

lun1: Path A/failover/failback
lun2: Path B/failover/failback
lun3: Path A/failover/failback
lun3: Path B/failover/failback

and so on ?

Re: About EVA 5000 with Secure Path

Uwe Zessin — Wed, 09 Feb 2011 18:05:00 GMT

You're changing controller ownership (=preferred path setting in CV_EVA) for a *virtual disk*. Technically, LUNs are created when presenting virtual disks to one or more hosts.
Yes, I know that the HP documentation sometimes calls a virtual disk a LUN.

The correct failover setting (failover-only or failover-failback) depends on the controller firmware, OS (version), multipath software and so on.

But yes, what you wrote is the basic idea.

Re: About EVA 5000 with Secure Path

RogerVI — Thu, 10 Feb 2011 22:14:26 GMT

Thanks

Re: About EVA 5000 with Secure Path

RogerVI — Thu, 10 Feb 2011 22:14:53 GMT

Thanks