Flash Storage​

Hi Abhishek,

One of the use cases which I implemented is to un-map a port from the VSM. If you have done GAD through CCI then you know we need to reserve resources (LDEV, ports) to the VSM (Virtual Storage Machine). Now if you want to un-map any of the ports from the VSM then we need to use virtual port id, please see the below example:

 Note: Here the port CL1-A-213 is already a part of a VSM.

@Abhishek Saxena - This command is necessary for setting up global-active device. It allows you to put a port (and volumes and host groups) in a Virtual Storage Machine. This makes the port (volume/host group) take on a different serial number and storage system model than the physical serial number and model. The end result is this enables servers to see volumes from two storage systems as different paths from a single storage system.

See this blog for more details on GAD: https://community.hitachivantara.com/discussion/global-active-device-best-practices.

Thank you @Dang Luong @Prasenjit Chatterjee for your insights.

Looking at the GAD user guide, I understand that simply reserving the hostgroup and LDEVs in VSM should suffice for creating a GAD pair.

The virtual information needed by the server to identify the S-VOL as additional paths doesn't list "port":

In what scenarios would we need to specifically reserve a target port? Also, what advantage does adding a virtual port ID has?

Thank you!

Abhishek Saxena

Thank you @Dang Luong and @Prasenjit Chatterjee for your insights, they are helpful.

Looking at the GAD user guide, it appears that reserving Host groups and LDEVs to the VSM should suffice to setup a GAD pair.

Additionally, the virtual information needed by server to see S-VOL as additional paths is listed in below table. It doesn't depend on port.

Wouldn't reserving a port to a particular VSM prevent meta_resource and other resource groups from accessing and using it?

Thank you!

Abhishek Saxena

Hi Abhishek,

You asked the below question in your last response:

Wouldn't reserving a port to a particular VSM prevent meta_resource and other resource groups from accessing and using it?

Ans: You reserve a port by its ID not by the port actually, as an example a port can have 256 IDs' from 0-255, so if you are reserving a port CL1-A-10 to the VSM then that same CL1-A-10 can't be in the meta_resource group, but same port with different id i.e. CL1-A-11 can belong to the meta_resource and you can have different host groups on same port but on different IDs'. Hope this will help you to understand how it works. Let me know if you have any additional question on this.

Good Day @Prasenjit Chatterjee, My understanding was similar to yours. I just call them HostGroup IDs, for example CL1-A-10 refers to the Host group with ID 10 on port CL1-A.

Coming to this particular thread, When I am talking about Virtual Port number, I am referring to the actual Port number being virtualized, not the Host Group IDs which you referred.

Take a look at this command description in CCI guide: 

Raidcom map / unmap resource command does accept -port and -virtual_port numbers, not the IDs:

Example: 

This is what I am trying to gather more information on. Where does applying a virtual port number on a physical port number helps  :)

@Dang Luong - I definitely didn't expect that. Anyway, great finding and thank you for all the help.