#Create a new stack and extending an existing stack

1 messages · Page 1 of 1 (latest)

tiny raft
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We are adding a new SSD shelf 1X DS224C onto existing 2xA700s controllers. Should we extending a stack or create a new one and why?

Currently there are only total of 2 shelve for the pair.
Please see attached the output of "sysconfig -a" from the node.

📎 message.txt
copper oar
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Message originally from @narrow aspen. The spam filter ate it 😕
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My observations

Shelf 0 is possibly configured for quad path ha and shelf 1 is multi path-ha.

In either case with two cards your best practice is to have each shelf connected with at least one path to each card. If a SAS card fails you will currently lose the whole shelf. Improve the resiliency.

Next, I’m not entirely sure that is a supported configuration (one shelf with 4 connections and one shelf with 2).

If I were cabling that shelf I’d end up with something like

Node 1 0a -> shelf 0 iom a1
Node 1 4d -> shelf 0 iom b3
Node 2 0a -> shelf 0 iom b1
Node 2 4d -> shelf 0 iom a3

Node 1 0d -> shelf 10 iom a1
Node 1 4a -> shelf 10 iom b3
Node 2 0d -> shelf 10 iom b1
Node 2 4a -> shelf 10 iom a3

The next two shelves would be:

Node 1 4c -> shelf 20 iom a1
Node 1 0b -> shelf 20 iom b3
Node 2 4c -> shelf 20 iom b1
Node 2 0b -> shelf 20 iom a3

Node 1 0c -> shelf 30 iom a1
Node 1 4b -> shelf 30 iom b3
Node 2 0c -> shelf 30 iom b1
Node 2 4b -> shelf 30 iom a3

This configuration would allow for 4 shelves to be connected as single shelf stacks.

It is entirely possible to make two stacks of two shelves each and still do quad path.

Node 1 0a -> shelf 0 iom a1
Node 1 4a -> shelf 0 iom a2
Node 2 0a -> shelf 1 iom b1
Node 2 4a -> shelf 1 iom a2

Node 1 0d -> shelf 1 iom b3
Node 1 4d -> shelf 1 iom b4
Node 2 0d -> shelf 0 iom b3
Node 2 4d -> shelf 0 iom b4

Shelf 0 iom a3 -> shelf 1 iom a1
Shelf 0 iom a4 -> shelf 1 iom a2
Shelf 0 iom b3 -> shelf 1 iom b1
Shelf 0 iom b4 -> shelf 1 iom b2

Node 1 0c -> shelf 10 iom a1
Node 1 4c-> shelf 10 iom a2
Node 2 0c -> shelf 11 iom b1
Node 2 4c -> shelf 11 iom a2

Node 1 0b -> shelf 11 iom b3
Node 1 4b -> shelf 11 iom b4
Node 2 0b -> shelf 10 iom b3
Node 2 4b -> shelf 10 iom b4

Shelf 10 iom a3 -> shelf 11 iom a1
Shelf 10 iom a4 -> shelf 11 iom a2
Shelf 10 iom b3 -> shelf 11 iom b1
Shelf 10 iom b4 -> shelf 11 iom b2

leaden moat
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Based on the output, this is an AFF A700s system. As such, all internal drives will be reported 4x times due to internal drive connections to the midplane.

#

Since you already have an external shelf attached, you can certainly attach a second without any issues. But on AFF systems, you cannot exceed more than 4x shelves per stack.

tiny raft
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@leaden moat @narrow aspen Yes, one shelf is internal, the other is external. I have some follow-ups, if you can please let me know:

  1. Do we currently have 2 stacks or 1 stack?
  2. Since we already have an external shelf (or an existing stack?) attached, will the new shelf just be added into the chain (or extending the existing stack) ?
  3. There is the other pair of 2xAFF A700 controllers in the same cluster with total of 5 shelve. Should we add the new shelf into this A700's HA OR that A700s' HA?
leaden moat
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  1. 2 stacks: internal and external. In addition to 24 internal drives, AFF A700s controllers support a maximum stack depth of four fully populated external shelves.
  2. Yes, absolutely.
  3. Another HA pair of A700 or A700s in the same cluster? You have expansion room on this HA pair of A700s controllers, so you're free and clear to attach one to it without disruption.
tiny raft
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My understanding is that A700 can support more shelve which is the only difference between A700 and A700s, that was why I asked if we should add the new shelf into A700 HA instead of A700s as what we are going to do...

leaden moat
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Ultimately, that will come down to your preference. You have expansion room on the HA pair of A700s, but also have room of on the A700 HA pair. Either way, do not exceed a maximum of 4x shelves per stack.