ONTAP Hardware

IOM12 and IOM6 mixed stack path throughput

pedro_rocha
389 Views

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

1 ACCEPTED SOLUTION

SpindleNinja
353 Views

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?   

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6 REPLIES 6

Ontapforrum
382 Views

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

pedro_rocha
369 Views

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

SpindleNinja
354 Views

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?   

pedro_rocha
306 Views

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

 

"

JonathanGaudette
287 Views
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.

Amador
177 Views
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