topic Re: Splitting a stack in ONTAP Hardware

Splitting a stack

netrz — Fri, 15 Mar 2019 15:37:08 GMT

Hi,

we have a 8020 HA-filer, both controllers have an additional 12Gbps 4-port expansion card.

- Stack 1 is a single DS224 Shelf (double IOM12).

- Stack 2 consits of one DS4243 (double IOM3) and two DS4246 (double IOM6). Both stacks are cabled with multipath HA to both FAS controllers.

If we add another 12Gbps 4-port expansion card per controller (which is also 6 Gbps capable) we have a total of 4 expansion cards, each with 4 ports = sixteen 6/12 Gbps SAS ports. This would be enough to make a multipath HA configuration for each shelf.

Would it be possible to split Stack2 up into 3 stacks, so each of its three Shelfs is its own stack without loosing the aggregate on this stack? (We can power down both filers for conversion.)

Additionally the IOM3 modules of DS4243 wouldbe replaced with IOM6 modules.

Re: Splitting a stack

aborzenkov — Fri, 15 Mar 2019 16:23:35 GMT

Yes, within HA pair you can rearrange shelves (and disks) as you like.

Re: Splitting a stack

CHRISMAKI — Fri, 15 Mar 2019 20:19:01 GMT

Thanks to software-based disk ownership, as netrz mentioned, this is fine.

The math around stacks is easy and is as follows: Each stack requires two ports per controller, ie: four in an HA-pair for MPHA.

A FAS8020 equipped with 2 x 4-port SAS cards per controller, along with its on-board ports would have 10 SAS ports per controller and could have up to 5 stacks of disk. The limit however of 480 target devices (disks/SSDs/LUNs) still exists and is a hard limit.