Disk shelf / Multipath / Loop Ids....

[nsitps1976]

Are loop IDs something you set or not? How do loops, shelf etc  relate to disk numbers???

Also can I check this is the correct cabling config as I can’t find reference to a single shelf loop:

2020HA + a single DS14MK2AT

2020 Cont A e0a > DS14 Cont A IN

2020 Cont B e0a > DS14 Cont B IN

Single path

2020 Cont A e0b > DS14 Cont B OUT

2020 Cont B e0b > DS14 Cont A OUT

Multipath

This is the first FC shelf (with netapp) I have had to install (only worked with DS4324 SAS)

[aborzenkov]

Yes, you have to manually set IDs on DS14 shelves. They must be unique within a loop (or, better, stack, as MP-HA has strictly speaking two loops) because they determine physical disk address on AL. Usually you start with 1 (0 is not allowed) and go up as you add shelves.

Your cabling example is correct.

[nsitps1976]

Thanks for the assistance.

I understand that disk shelfs need to have their ID set but what about actual loops? Do they have IDs which need to be set or not? Also, how does the loop #, shelf # relate to the disk numbering?

[aborzenkov]

Loops are named according to FC adapter. So disk on a loop connected to FC adapter 0b will be 0b.NN, where NN is computed from shelf number.

In case of multipath system arbitrarily selects which path is used to name disk. So some will appear on 0a, some on 0b. You can use “storage show disk –p” to display both pathes.

[nsitps1976]

So in my example there will be two loops (due to MP HA), namely 0a and 0b??????

Disks will be numbered / named as follows?

Loop ID (0a), shelf ID (2), disk 0 – 13????

Eg: 0a.2.13 for the last disk in shelf 2 (one being the head as it has disks installed) on loop 0a???

[aborzenkov · Accepted solution]

Disk number is 16*shelf_id + slot_id

So disks in shelf 2 will be 32 .. 46; i.e. 0b.32, 0b.33, etc

[nsitps1976]

Great thanks for the help.

Last question, how are the disks in the storage system head numbered then? I know the system has shelf ID1 in this senario, howerver they are not attached to 0a or 0b???

[aborzenkov]

Internal disks are SAS not FC; so they are connected to another, SAS, adapter. SAS shelves have independent numbering (OK, in case of 2020 you cannot connect any external shelf, still rule applies).