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ask about growth increment where create CPG

 
nguyenhuukhoi
Occasional Contributor

ask about growth increment where create CPG

Hello guys,

I am new with SAN 3par 8000. I read docs but i still dont understand about growth increment where creating CPG! Could u give me an example about using it?

many thanks

7 REPLIES
HPEStorageGuy
Neighborhood Admin

Re: ask about growth increment where create CPG

A good resource to learn more is the 3PAR Concepts Guide.  There's a section on page 39 focused on CPGs. 

I also asked some of my 3PAR experts about your question.  Here's what I heard back:

From a best practice standpoint if it is a CPG for HDD drives it should be left at the default. 

If it is a SSD CPG the following is the best practice.

Best practice: The growth increment should be set to the minimum value, which is 8 GB per node pair. On two node systems, set the value to 8 GB, on four node systems to 16 GB, on six node systems to 24 GB, and on eight node systems to 32 GB. In order to set the CPG growth increment to a lower value than the default, the “show advanced option” box must be checked.

Hope that helps!

Sheldon Smith
Honored Contributor

Re: ask about growth increment where create CPG

A CPG sets the rules for how a specific group of logical disks are created and expand. The growth increment is automatically used whenever more storage capacity is needed by the logical disks.
As a general rule, the default growth increment values work best.
A hybrid system with a relatively small amount of flash storage may use a minimum value for the flash CPG growth increment, see the createcpg command in the HPE 3PAR OS Command Line Interface Reference.

The HPE 3PAR StoreServ Storage best practices guide also recommends using as few CPGs as possible.

See the Hewlett Packard Enterprise Information Library, http://h17007.www1.hp.com/us/en/storage/info-library/index.aspx for all documents mentioned in this thread. As my colleague HPEStoreageGuy wrote, read the Concepts Guide.


Note: While I work for Hewlett Packard Enterprise, all of my comments (whether noted or not), are my own and are not any official representation of the company.
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nguyenhuukhoi
Occasional Contributor

Re: ask about growth increment where create CPG

Thank you, But can you give me a detailed example? I have read docs, however i am not image how about it!

Dennis Handly
Acclaimed Contributor

Re: ask about growth increment where create CPG

> I have read docs, however I can't imagine how to go about it,

 

It should be clear:

createcpg ... -sdgs <size>G cpgname

Where the minimun size is based on the number of nodes, 8, 16, 24, 32.

For an existing CPG, you can use the similar command setcpg.

Sheldon Smith
Honored Contributor

Re: ask about growth increment where create CPG

>  ... I can't imagine how to go about it,

Go about what?
Any time a virtual volume associated with the CPG needs more space than is currently available in the CPG, the CPG automatically adds an increment's worth of storage to the CPG and then allocates the required space from the CPG to the virtual volume.

You don't do anything. When a CPG is created, it has a default increment size. Leave the default where it is.


Note: While I work for Hewlett Packard Enterprise, all of my comments (whether noted or not), are my own and are not any official representation of the company.
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ashraf_islam
Advisor

Re: ask about growth increment where create CPG

one query : what is the purpose of growth increment in CPG?  please clear  this point.

Dennis Handly
Acclaimed Contributor

Re: ask about growth increment where create CPG

@ashraf_islamwhat is the purpose of growth increment

 

It's a performance knob.  If you are going to be growing a lot, you want to get a big increment.

If not growing a lot or you're short on space, you may want a smaller value.