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Confused between HP 3PAR HA CAG and Spare Maximal?

 
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Khurram exe
Contributor

Confused between HP 3PAR HA CAG and Spare Maximal?

Hi All,

 

I am new to HP3par and i have read that 3par sparing has three options Default, Minimal & Maximal.

 

The Maximal states that

"Maximal: Allocates one disk worth of spare chunklets per drive cage of the largest size disk in thesystem to provide cage level high availability"

 

In addtion to that while creating CGP it gives you the option of HA Cage to survive cage failure.

 

So i have three questions?

 

1- If Maximal sparing gives you cage level high availbity than what is the purpose of HA CAGE while creating CPG. I am confused between the two concepts?

 

2- Secondly I have StoreServe 7200 with two drive enclosures, my volumes would be RAID 1 and RAID 5 can i use HA Cage to protect my volumes?

 

3- What is the HA Port?

 

Regards!

KS

 

3 REPLIES
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Re: Confused between HP 3PAR HA CAGE and Spare Maximal?

>1- If Maximal sparing gives you cage level high availability than what is the purpose of HA CAGE while creating CPG.

 

They are two different concepts that have to work together.

1) -ha cage lays the chunklets out so that the RAID sets are on different cages.  If a cage goes out, there is at least one copy left to serve data.  But in a degraded and non-protected state.

 

2) While the cage is out, the system copies each chunklet to a spare so that if a PD goes bad, there is another copy.

And if a cage goes out, you would need lots more spare chunklets to make the copies.

 

>2- I have StoreServ 7200 with two drive enclosures, my volumes would be RAID 1 and RAID 5 can I use HA Cage to protect my volumes?

 

Yes for RAID 1.  I think you need more cages for RAID 5.

 

>3- What is the HA Port?

 

I was told that if you have cages daisy chained, then it protects against a port failure losing more then one cage.

Khurram exe
Contributor

Re: Confused between HP 3PAR HA CAGE and Spare Maximal?

Hi Dennis, 

 

Thanks for your detailed reply, Now i  have understood the concept.

 

=============

One Last query

=============

Can we later change the HA settings in CPG and sparing option once set?

 

Secondly before writing to spare 3par uses logging disk, what is the size of that disk and any recommendations of size?

 

Thanks!

 

Regards, 

 

KS

Re: Confused between HP 3PAR HA CAGE and Spare Maximal?

>Can we later change the HA settings in CPG and sparing option once set?

 

setcpg will allow you to change the -ha option.

You can use createspare/removespare to add/remove spare chunklets.

 

>logging disk, what is the size of that disk and any recommendations of size?

 

You don't have control over logging LDs.