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Can anyone explain HP 3PAR CPG "Availablility": Cage, Port, Magazine ?

 
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StuartA46
Frequent Advisor

Can anyone explain HP 3PAR CPG "Availablility": Cage, Port, Magazine ?

When I create a CPG in the Inform Management Console, it asks me for "Availability", and the choices are "Cage", "Port" and "Magazine".  How does that influence how the chunklets are spread across the disks?

 

I think that "Cage" means that he takes one chunklet from every "cage" across all of the disk cages on the node-pair.  Is that right?  Then he comes back around and takes another chunklet from the same cage again, etc.

 

So what do "port" and "magazine" mean?

 

We have 2 x node pairs each with 4 x cages.  Each cage has 10 x magazines, each magazine has 4 x disks.

5 REPLIES

Re: Can anyone explain HP 3PAR CPG "Availability": Cage, Port, Magazine?

>I think that "Cage" means that he takes one chunklet from every "cage" across all of the disk cages on the node-pair.

>So what do "port" and "magazine" mean?

 

From the HP 3PAR InForm OS 3.2.1 Command Line Interface Reference:

http://h20566.www2.hp.com/hpsc/doc/public/display?sp4ts.oid=5044394&docId=emr_na-c04204279&docLocale=en_US

 

createvv createcpg createtemplate setcpg showspace

–ha port|cage|mag
Specifies that the layout must support the failure of one port pair, one cage, or one drive magazine (mag). This option has no meaning for RAID-0.

StuartA46
Frequent Advisor

Re: Can anyone explain HP 3PAR CPG "Availability": Cage, Port, Magazine?

Thanks for answer.  I understood that already.  The question is how does the selection of -ha cage | port | mag affect the distribution of chunklets on the disks?  Obviously cage means that the chunklets are distributed across different cages.  Then "port" must mean that the chunklets are distributed across different port pairs; and "mag" must mean that the chunklets are distributed across different magazines?  Does that sound right to you?

 

But let me ask you a question:  Let's say I pick "mag".  Do the chunklets distribute to the next mag in the same cage, or do they go to a mag in the next cage? 

 

As near as I can tell, this isn't explained anywhere. 

 

   Stuart

Solution

Re: Can anyone explain HP 3PAR CPG "Availability": Cage, Port, Magazine?

Cage enforces taking each chunklet for a given RAIDset from separate disk cages/chassis/shelves. Port makes sure each chunklet comes from different ports. For a T or V class, Cage and Port are the same thing.

Magazine enforces taking each chunklet from separate magazines. Which magazine? You don't care. (Not documented.) That's why you specified "-ha mag".


Note: While I am an HPE Employee, all of my comments (whether noted or not), are my own and are not any official representation of the company.
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Re: Can anyone explain HP 3PAR CPG "Availability": Cage, Port, Magazine?

>Does that sound right to you?

 

Yes.

 

>Let's say I pick "mag".  Do the chunklets distribute to the next mag in the same cage, or do they go to a mag in the next cage?

 

If you only pick mag, then I assume it doesn't really matter where they are placed, as long as not the same one.  The OS is free to pick based on what's free, what's fastest, etc.

 

 

 

giladzzz
Honored Contributor

Re: Can anyone explain HP 3PAR CPG "Availability": Cage, Port, Magazine?

Hi

Availability means what happens in case of failure

'cage means the CPG will survive cage failure port means port failure and magazine means 

magazine failure

Zohar