topic Re: We have stack of 6 DS2246 disk shelf ,planning to add 1 DS4243 disk shelf in ONTAP Hardware

We have stack of 6 DS2246 disk shelf ,planning to add 1 DS4243 disk shelf

kushaalk — Wed, 04 Jun 2025 13:23:20 GMT

Hi Team,

We have Stack of 6 DS2246 disk shelf connected to FAS3210 running 8.2.4 7mode,we are planning to add 1 DS4243 disk shelf.

Willing to know if connecting DS4243 make entire stack to serve at 3gbps,we have data serving on DS2246 so confirming .
Is there way to confirm what is current backend bandwidth utilization on netapp.

From compabiltiy point am sure it works,only worried about perforamce

Re: We have stack of 6 DS2246 disk shelf ,planning to add 1 DS4243 disk shelf

aborzenkov — Fri, 24 Aug 2018 13:23:10 GMT

According to my information, yes, stack speed will be throttled down to the slowest IOM.

Re: We have stack of 6 DS2246 disk shelf ,planning to add 1 DS4243 disk shelf

naveens17 — Fri, 24 Aug 2018 14:41:55 GMT

just curious to know if there are no additoional SAS ports avaiable on the controller

Re: We have stack of 6 DS2246 disk shelf ,planning to add 1 DS4243 disk shelf

andris — Tue, 28 Aug 2018 17:24:31 GMT

An easy way to fix the mismatch would be to purchase 2 x IOM6's to swap out with the IOM3's - ONTAP will essentially treat it as a DS4246 (even if the HDD's themselves are 3Gb/s SAS.).

If you don't go that path, it's not really a blanket statement that everything is throttled down to 3Gb/s on the stack.

SAS is a point-to-point protocol. The speed of a connection during its duration will depend on the components in the path of the connection.

If the path goes through a IOM3 in the DS4243 shelf or terminates on a 3Gb/s HDD/drive, then the connection for that I/O transaction will run at 3Gb/s.

If the path to a 6Gb/s drive only has 6Gb/s components in it, then the transaction is at 6Gb/s.

Let's assume that you have multi-path HA cabling (MPHA) and you put the DS4243 at one end of the 7-shelf stack.

ONTAP will choose the "shortest path" to the HDD/drive.

This will mean that 4 of the shelves will be accessed from one end of the stack while the other 3 will be access from the other end of the stack (again, assuming you have properly cabled for multipath HA (MPHA).

So, this means that 4 of the 7 shelves will be able to form SAS connections at 6G/bs speeds 100% of the time. The other 3 (including the DS4243) will run with 3Gb/s connections if the path goes through the DS4243 first (at the end of the stack).

Having said all that, I doubt you'll see any tangible performance difference, anyway. Even 3Gb/s SAS is 4 x 3Gb/s lanes = 12Gb/s bandwidth for that path to the 3 shelves from each controller's SAS HBA port.