LUN ownership/allocation - Urgent help requested

[Chris Rasmussen [FAU]]

Hi all,

Sorry for the urgent title - this relates to a change happening tonight so I hope someone can help.

One of our EVA 8000 controllers needs to be rebooted due to an HP recommendation.

Can I *manually* tell the LUNs that are currently owned by that controller to be managed by the other controller?

I'm trying to prevent all the LUNs owned by the controller being rebooted from moving to the other controller in one go.

Thanks!

[Uwe Zessin]

You can change this on each virtual disk's [Presentation] tab.

[Chris Rasmussen [FAU]]

I know about that but does that then mean that "Path A" means Controller A and that setting the LUN to use Path A will force it to use *Controller A* if available?

[Uwe Zessin]

Correct.

Unfortunately, many terms are used in an ambiguous way and that makes conversations ... 'interesting':

- 'path preference' vs. controller ownership
-- (usually, you have multiple paths (host FC ports to EVA controller ports))

- LUN vs. virtual disk

- LUN IDentifier/number vs. LUN address

...

[Chris Rasmussen [FAU]]

Well, by controller ownership I simply meant the managing controller as indicated by CV.

I was 95% sure of the answer already but wanted to make sure because, as you know, the controller labelled "Controller A" isn't necessarily the *master* controller ... perhaps the managing controller isn't the same as the controller that owns the vdisk.

If that makes sense that is, sorry if not. :)

[Uwe Zessin]

Yes, I understand.

The "Controller A" (or "1") name is set when the EVA is initialized, but can be changed later.
It is usually the physical top controller, but need not be.
CV-EVA might list it _below_ the "B" controller, even if physically on top.


One controller in an EVA system is the "master" controller and the other is the "slave" controller ...
except when the firmware became confused and there is no master controller any longer ... then, CV becomes confused, too :-( ... then, the user becomes confused, too :-( :-(


A virtual disk is 'managed'/'owned' by one controller at a time, but this function can be transfer to the other controler later. The managing/owning controller might be the master controller XOR the slave controller. A different virtual disk can be managed by the same or the other controller.
(I never use the term 'master controller' when I mean 'managing controller of a virtual disk')


I hope we got to 96% at least, not less than 95% ;-)

[Chris Rasmussen [FAU]]

And unfortunately HP doesn't publish how to find out which controller is the master and which is the slave although I think most EVA administrators know how to find out. ;-)

I found out that manually moving a vdisk from one owning controller to the other isn't an officially supported HP action anyway so doing this isn't a good idea unless it's discussed with HP first. It's for similar reasons to why they stopped displaying the RSS disk state - it's not a user-manageable piece of info.

XCS calculates load based on the number of vdisks too, not the load applied to each one so unfortunately sometimes the load can become uneven - moving vdisks is then supported, I think.

I think we're even at 97% now! ;-)

[Uwe Zessin]

The master/slave information can be queried through the (W)OCP. It doesn't seem to be in the end-user accessible CV/SSSU areas.

The EVA was never intended to offer 'micro-management features' and for many normal work environments one does not need to know about the master/slave controllers or do any tuning.

This isn't sufficient when problems come up or when the 'Outstanding self-tuning performance' ( http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=c00365590 ) falls a bit short due to unfortunate blancing (e.g. forced by VMware hosts who often use the first path found for all disk access so all vdisks end up being managed by one controller) or internal implementation restrictions.

Here, the user base gets very little support except for a few helpful HP employees or some 'breadcrumbs' in the form of a customer advisory from time to time.

[Chris Rasmussen [FAU]]

Yeah, it's not in the end-user accessible CV/SSSU areas ... you just gotta know where to look (which I'm sure you do). ;-)

My main wish would be for HP to release some of the internal reporting tools ... sigh.

[Chris Rasmussen [FAU]]

Uwe helped again by clarifying a number of relevant points. Thanks!