Tuesday, 5 June 2012

NetApp: FAS2040A Walkthrough Setup & Install Notes Part 3/5 – Disk Ownership and RAID Setup


The FAS2040A (Dual Controller Model) utilizes an Active-Active HA pair of controllers. Each controller head must have disk ownership of the disks on which its own root volume sits. In a fail-over situation, the remaining cluster head will take over the 'virtual' identity of the failed head with its igroups, LUN mappings, etcetera.

Out of the factory, the FAS2040A is configured similarly to the diagram below:
Key:
A = Controller A
B = ControllerB
D = Data Disk
P = Parity Disk
dP = Double Parity Disk
S = Spare
X = Unowned

Only 2 of the available disks are available for data (1 data disk per controller), and the available data space also contains the root volume /vol/vol0

In the scenario where we have a FAS2040A with 12 disks, and no available disk shelf, below are some options available

Option 1: Utilizing Each Head Equally
In the above option, we can either have 6 disks available for data (3 on each controller) if require to keep a hot spare on each controller, or can have 8 disks available for data (4 on each controller) if it is not required to keep a hot spare on each controller.

Option 2: Going For As Large A Volume As Possible
In the above option, we can have either 7 disks available for data (6 on one controller, 1 on the other) if require to keep a hot spare with the main controllers pool of disks, or can have 8 disks available for data (7 on one controller, 1 on the other) if do not require to keep a hot spare with the main controllers pool of disks.

Note 1: RAID-4 (which has only one parity disk) is not considered here as it is not possible to disable the alarm for no available spare if using RAID-4. Also, for doing no disruptive disk firmware upgrades, need to be on RAID-DP, and it is preferable to have a RAID-DP than a RAID-4 with hot spare.

2 comments:

  1. Thank you for interesting article,
    Is it possible to detail how to get from Factory setup to Option2? on FAS 2040 by default aggregate where root volume resides consists of tree disks that are odd numbered.How can I rearrange the underlying disks?

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  2. Hi Daugavpils,
    I'd check out my post on the simulator:
    http://cosonok.blogspot.co.uk/2011/12/netapp-simulator-81-walkthrough-setup.html
    And also Julian Wood's (goes into reallocating disks):
    http://www.wooditwork.com/2012/01/04/installing-maximising-the-netapp-ontap-8-1-simulator/
    Cheers,
    VCosonok

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