SAS Cabling - from 2 stacks to 1 stack

[gavin_meadows]

We just had 2 2246 shelves installed onto a 3140 HA pair.  Each controller has 1 quad port sas card installed.

The disks are all currently unassigned but I have noticed that all 4 ports have been used on each SAS card on each controller.

It looks like the shelves have been added as 2 stacks containing 1 shelf.

my preference would be to have a single stack of 2 shelves, I've checked the cabling and I can remove the redundant path for each stack while still having a connection from each controller to each shelf.

This will free up the correct IOM circle and square ports for me to link the shelves together and create a single stack, but I don't know how the controllers will react?

Is this safe to do transition from 2 stacks to a single stack in this manner? how will it affect the disk namesd etc? These SAS disks are all currently unassigned but we have other FC disks in production on this SAN so I want to be sure there will be no issues,

many thanks

Gavin

[aborzenkov]

You will need to change cabling offline (controllers shutdown). But I do not see any reason to do it. The more HBA IO is distributed over, the better. The only reason would be if you plan different shelf type.

[gavin_meadows]

It is very possible we will add different shlf types in the furure so i would like to keep my options open.

This is how they were originall cabled:

I have removed the redundant paths in blue so it
is currently like so:

This has freed up the necessary
circle and square ports to interconnect the shelves like so:

Are you saying the filer needs to be completely shut down before making this interlink connection between the shelves - can you elaborate on the reasons for this?  I had hoped that it would just pick up the new redundant paths.

The shelf ID's have always been 1 & 2 and all disks have been 'unassigned' since the shelves were added.

(I know I also need to change filer1 4B to 4D)

[gavin_meadows · Accepted solution]

Ok so I ran the plan by Netapp Support and they saw no issues in doing it:

Cable Shelf 1 to shelf2 IOMA

Cable Shelf 1 to shelf2 IOMB

Confirm with storage show disk –p

Controller 1, move port 4b to port 4d

Confirm with storage show disk –p

Perform takeover and giveback in both directions

successfully executed last night,

Gav