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How to select the disks from Different controllers in EVA8K

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Rath Kum
Frequent Advisor

How to select the disks from Different controllers in EVA8K

Hi

How can we create Vdisks from same Controller(Say Controller A). I dont see any option to choose when creating Vdisk in CV!
I am creating a DR group and reading instructions from the manual says :
"A DR group can contain virtual disks from multiple disk groups, but all DR group member virtual disks must be in the same array and must be preferred to the same controller on the array"

Can any one explain? your help will be appreciated

Thanks








8 REPLIES
Steven E. Protter
Exalted Contributor

Re: How to select the disks from Different controllers in EVA8K

Shalom,

Not sure what you are trying to do is relevant on EVA. The system load balances between controllers anyway, and LUN creation is from a GUI interface.

The array is designed to present all configured luns even if a controller fails.

SEP
Steven E Protter
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Rath Kum
Frequent Advisor

Re: How to select the disks from Different controllers in EVA8K

SEP

Thanks for your quick reply

I just dont understand what does it mean -

DR member virtual disks must be preferred to the same controller on the array " and "all members of a DR group must share
a preferred controller, therefore load balancing a single application with all of its virtual disks in a single DR group (as required) across multiple controllers, is not possible"
from the above statements .
Can u please explain ?

Thanks



Rob Leadbeater
Honored Contributor

Re: How to select the disks from Different controllers in EVA8K

Hi,

You can configure a Vdisk with a Preferred Controller, which is what it sounds like you need to do.

If I remember correctly, this option can be found under the Presentation tab for each Vdisk.

Hope this helps,

Regards,

Rob
Rath Kum
Frequent Advisor

Re: How to select the disks from Different controllers in EVA8K

Hi Rob

I just checked under presentation tab , it is automatically selected Managing controllers for vdisks (some as controller A and some other as Controller B)
I dont see any option to select the controllers !

Thanks
IBaltay
Honored Contributor

Re: How to select the disks from Different controllers in EVA8K

Hi,

If we are speaking on the ILT switched off in CA, then the reason is nicely described here:
http://www.frankdenneman.nl/?p=5

abstract:
All LUNs in a DR group fail over together, share a log and preserve write order within the group. Because one controller manages a group of LUNs, EVA firmware XCS 6.1 (and up) disables implicit LUN transitions for all DR group members.

Mixing Implicit LUN transition (ILT) together with a large DR group can be a recipe for disaster. Imagine if the array detects too much proxy reads on a LUN in the group. The array will evoke a ILT. Because they form a group, all members are transitioned together. So far so good, but you can bet on it that a new proxy read situation appears, due to the multiple hosts communicating with the disks. This will evoke another Implicit LUN transition. And now we are back where we started. Enabling Implicit LUN transition can create some sort of bouncing group of LUNs between controllers
the pain is one part of the reality
IBaltay
Honored Contributor
Solution

Re: How to select the disks from Different controllers in EVA8K

if we are not speaking on the CA, then you can set NONE or all variants of SET PREFERRED PATH TO CONTROLLER A or B (failover only, failover and failback,...) to each VDISK individualy during the VDISK presentation
the pain is one part of the reality
Rath Kum
Frequent Advisor

Re: How to select the disks from Different controllers in EVA8K

you are right. Thanks for your help
Rath Kum
Frequent Advisor

Re: How to select the disks from Different controllers in EVA8K

Thanks everyone for your help.