MSA Storage

Re: MSA2040 and a/a, a/p , ALUA

Occasional Advisor

MSA2040 and a/a, a/p , ALUA

I have a lab setup with a msa2040, 4*FC with 8Gbit,

a direct FC link to a dl380G6 with a brocade dual Port adapter,

using both ports.


I configured a volume and gave the Conntroller B as the default controller.

I connected both FC cables to the 2 ports on Ctrl A.


Why does this configuration work ?


If the 2040 is a/a machine, what does the "default controller" mean ?

If a/a there is no need for such a configuration because of:


If the Server configures the Path to controller A as default path,

and the 2040 is configured to use B as default .... this is meaningless!!



i am confused about that ...


Or is this the way to configure load balancing between the controllers?


When B is default and only A is connected i should see at least


Preferred Owner:B

Current Owner:A



BUT i see


Preferred Owner:B

Current Owner:B


Thats the reason for my confusion.






Trusted Contributor

Re: MSA2040 and a/a, a/p , ALUA

MSA2040 storage system uses Unified LUN Presentation (ULP), which can expose all LUNs through all host ports on both
controllers. The interconnect information is managed in the controller firmware. ULP appears to the host as an
active-active storage system where the host can choose any available path to access a LUN regardless of disk group
ownership. When ULP is in use, the controllers' operating/redundancy mode is shown as Active-Active ULP. ULP
uses the T10 Technical Committee of INCITS Asymmetric Logical Unit Access (ALUA) extensions, in SPC-3, to
negotiate paths with aware host systems. Unaware host systems see all paths as being equal.

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Acclaimed Contributor

Re: MSA2040 and a/a, a/p , ALUA

In other words ... in a classic MSA2000 a controller is the owner of a vdisk and handles all data there. This controller can pass-thru thr data to the other controller, but this is slower, or can hand over the ownership for some reason. The other controller is owner of the next vdisk, so the controllers are a/a, both are working, there is no standby only.

Hope this helps!

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