Disklayout 7200 3par

[Darking]

Hello All.

We have bought a Nice 7200 array! Hurray.

Before our solution provider comes by the datacenter I'm racking up the controller and its 3 extra m6710 chassis.

After reading the installation guide I'm a bit confused about the initial disk layout. The guide states that disks should always be installed in pairs. I sort of assume its due to minimum redundancy requirements, but when I ordered the array my provider Also included an IOPS and disk layout.

They have it like this:
Chassis1(control unit):0-7 SSD, 8-17 SAS
Chassis2: same as chassis 1
Chassis3:0-5 SSD, 6-13 SAS
Chassis4:same as chassis3


To me it makes more sense to give all 4 chassis the same configuration. Ie.
0-6 SSD, 7-15 SAS
In my view that would let me have cage level redundancy with raid5(3+1).

Am I missing something obvious?

Regards

Christian

[jburr]

You might want to look at the Site Planning Guide. The layout will likely depend upon your desired Raid levels and CPG configuration.

The planning guide gives you the minimum requirements for the different raid levels. Perhaps that was an influence on the design.

Just a thought.

[Cleanur]

Disks are as added in pairs as the system is symmetric active active, so each controller is given initial ownership of a disk, hence they need to be added in pairs. You just need to make sure even numbers of any combo are added per enclosure.

[Darking]

Thank you both.

I just wrote to my vendor, asking why they made an invalid design. They must be missing 4 SSD and 4 SAS from the deployment for it to be valid for cage redundancy.

[Brewer]

Raid 5 (3+1) i believe you need 32 of each disk type, 8 of each in each shelf.