topic Re: IOM12 and IOM6 mixed stack path throughput in ONTAP Hardware

IOM12 and IOM6 mixed stack path throughput

pedro_rocha — Wed, 04 Jun 2025 09:58:10 GMT

Hi,

When we have a stack with both IOM6 and IOM12 (maintaining one speed transition, as supported), does the paths to both beginning and end of the stack goes 6Gbps? Or it will have one side 12Gbps and the other 6Gbps?

Regards,

Pedro

Re: IOM12 and IOM6 mixed stack path throughput

Ontapforrum — Tue, 09 Aug 2022 15:32:18 GMT

Good one, I read this article and found it very useful. If I followed (article) it correctly, it appears that one-end will be 6 and other 12, maintaining a single transition. I guess considering it is 6-6-12, or 6-6-12-12, but not 6-6-12-6 or 12-12-6-12. Hopefully, what I am assuming is correct but cannot be 100% sure.

https://docs.netapp.com/us-en/ontap-systems/sas3/iom12-hot-add-mix.html#cable-shelves-for-a-hot-add

Re: IOM12 and IOM6 mixed stack path throughput

pedro_rocha — Tue, 09 Aug 2022 17:06:12 GMT

Hi, yeah.. I also saw that. It's not clear from the text...

Re: IOM12 and IOM6 mixed stack path throughput

SpindleNinja — Tue, 09 Aug 2022 20:42:25 GMT

I went to check on a system that is A300 -> DS2246 (IOM6) -> DS224c (IOM12) -> A300

Looking at "expander_phy_state" you can see the state of the drives -
There's a physical (physical connection) and logical (data rates) rates.

(Logical rate is the lowest common rate of all links.)

Drives in the DS224c look like -> "12.0 Gb/s(6.0)"

Drives in the DS2246 look like -> "6.0 Gb/s"

Looking at the connection from DS2246 IOMA Circle to DS224c IOMA (p1) to DS224c IOMA (p3)back to the controller it looks like this ->

0/P0:0 6.0 Gb/s          --- --- --- --- 0      0      0      1      0      1      ----------------
 1/P0:1 6.0 Gb/s          --- --- --- --- 0      0      0      0      0      1      ----------------
 2/P0:2 6.0 Gb/s          --- --- --- --- 0      0      0      1      0      1      ----------------
 3/P0:3 6.0 Gb/s          --- --- --- --- 0      0      0      0      0      1      ----------------

 8/P2:0 12.0 Gb/s         --- --- --- --- 0      0      0      0      0      1      ----------------
 9/P2:1 12.0 Gb/s         --- --- --- --- 0      0      0      0      0      1      ----------------
10/P2:2 12.0 Gb/s         --- --- --- --- 0      0      0      0      0      1      ----------------
11/P2:3 12.0 Gb/s         --- --- --- --- 0      0      0      0      0      1      ----------------

TLDR -

The stacks runs at the lowest common speed.

SAS3 to SAS3 runs at 12

SAS2 to SAS3 runs at 6

If you upgrade the DS2246s to DS2246-12 the stack will run at 12, while the backplane of the DS2246 remains at 6.

As far as helping make the doc more clear. What do you think would help? something related to Drive and stack speed while in a mixed SAS2-SAS3 stack?

Re: IOM12 and IOM6 mixed stack path throughput

pedro_rocha — Wed, 10 Aug 2022 14:19:12 GMT

Hi,

Thanks for the answer.

As far as for the doc improvement, I guess that having the words "The stacks runs at the lowest common speed" is sufficient.

Pedro

Re: IOM12 and IOM6 mixed stack path throughput

JonathanGaudette — Wed, 10 Aug 2022 17:38:50 GMT

One side will be 6gbit and one side with be 12gbit. If you had 6gbit at both ends, it would be two "speed transitions" and be considered incorrect.

Re: IOM12 and IOM6 mixed stack path throughput

Amador — Mon, 15 Aug 2022 13:40:14 GMT

I think we can cover this with How to cable an IOM12E platform with IOM6 and IOM12 storage shelves in Multi-Path HA - NetApp Knowledge Base