Best practice for rebalancing SAS connections?

[storage_ergo]

Hi,

I have a situation where a customer has maxed out all of the existing SAS ports on their system ( 2 quad port SAS HBAS). We will be adding a new Stack along with another SAS quad port HBA. Can I safely rebalance all the existing stack connections across the new card along with the existing cards? Is it reccemended to do so ? My concern is that it I were to use only the new HBA for the new stack, it  would be on a single card. Any thoughts ?

[korso]

As long as you have they don't have any more than 10 SAS-based disk shelves in any disk stack connected to the SAS ports, you should not have to "rebalance" the disk shelves.

I have provided the link for the "Universal SAS and ACP Cabling Guide" for your review which contains the best practices for cabling the shelves to the SAS ports on all NetApp FAS controllers.

https://library.netapp.com/ecm/ecm_get_file/ECMM1280392

If the they are wanting to still redistribute shelves, then I would follow the universal guide and balance out the shelves across all the available port. As always, contact NetApp support and create a ticket before doing any moves just to have support ready in case they run into trouble.

NetApp Global Support Center: 888-4NETAPP (888-463-8277) 

[storage_ergo]

Thank you for the reply. so the only drawback would be that the new stack is on the same card if I don't rebalance. Rebalancing is an option provided I have the proper measures in place i.e. Less then 10 shelves per stack, case open with NetApp etc.

[scottgelb]

Agreed a case for proactive troubleshooting. There is no hot maintenance on a controller to move source ports but it can be done in takeover mode. I do it fairly often with one node down them giveback and repeat on the partner controller. I boot to maintenance mode before giveback to make sure the ports see the disks/shelves.

[storage_ergo]

Great tip! I never thought of doing into maintenance mode to check paths, but it will be part of my procedure going forward. Thanks!

[scottgelb]

Don't be alarmed by the warning that the system is in takeover and any changes will cause issues... the only commands you will run are "sasadmin shelf" and/or "sasadmin expander_map" then do a halt, boot_ontap then cf giveback on the partner.