7MTT 3.0.0 SAS cableing requirments during cutover and leaving trays behind

[a_jasewicz]

I have questions about the cutover process and getting as much done in the scheduled outage as possible.

I have my cDOT 8.3.2P4 in a temporary rack, I have evacuated (7MTT copy based) and removed all my FIBER DS14-Mk4 shelves, save for one, from my 7-mode (8.1.4P9) which has the HA root vols/aggregates.

My cDOT has 2 stacks.

• Stack 1 DS2246 (4 trays) SAS
• Stack 2 DS4246 (2 trays) SATA

I would like to use the CFT option to move the remaining 7-mode trays consisting of

• Stack 1 DS4243 (2 trays) SAS + DS2246 (1 tray) SAS (3 trays total). Yes it’s a 3g to 6g transition in the same stack
• Stack 2 DS4246 (2 trays) SATA

I would like to power everything off, relocate the cDOT system to is permanent rack and create 3 stacks on the cDOT system and leave my old 7-mode root volume and tray behind.

So in the end

• Stack 1 = 5 trays -- DS2246 (4 from cDOT) + DS2246 (1 from 7-mode) - SAS
• Stack 2 = 2 trays -- DS4243 both from 7-mode - SAS
• Stack 3 = 4 trays -- DS4246 (2 from cDOT) + DS4246 (2 from 7-mode) -SATA

Tray attach questions)

- Is this possible or am I not able to add the 7-mode CFT trays to an existing cDOT stack?

- Is breaking up the 7-mode stack 1 an issue?

- Do I need to first move them (leaving the 7-mode stacking and order) to a new stack, and then re-cable (re-stack) them after they are recognized by the cDOT system?

- Is there doc available to describe what I am attempting?

Root volume/tray question

• I can ignore the root volume by adding this option to the CFT “transition cft ignorableerrors add -p <project-name> -c ignore-target-port-requirement”. Will this cause an issue, not having the tray  to attach to the cDOT system?

[a_jasewicz]

I may have answered my own question. From the Cabling guide, last page, "Consolidation of disk shelf stacks is not supported".  I guess that would be considered a "Consolidation".  So my follow up is When can I place these shelves into the stacks I want? after this step "Transition the aggregates and volumes on the migrated disk shelves to clustered Data ONTAP" or after the "commit"

[SeanHatfield]

The stack consolidation note is something thats spawned some internal discussion here, since we teach stack layout planning in the CFT class, including changing the stack layouts, shelf IDs, etc. Its being looked at.  The stack layout and cabling do need to adhear to the rules for MPHA cabling, shelf mixing, etc.  They shoud be labeled with the original shelf IDs and you should use the cabling worksheet to record the original stack layout and plan the new layout, in the event you need to rollback for some reason.

I have seen cases where they did power off everything during the cutover and re-rack the cluster with all the stacks the way they wanted them in between export & halt, and check cabling.  Not ideal, but possible.  The more physical rework you have to do, the longer the outage window needs to be to accomodate that work, and the longer it will take to rollback if the need arises.

Ignoring the port requirement will not allow you to leave the 7mode DS14 shelf behind during the cutover.  All shelves and disks present before export & halt need to be preset at the check cabling step on the destination system or you will not be able to proceed.  If you need to remove shelves from either the source or the destination, do it prior to the CFT project.  If your destination system cannot support the DS14 (FAS8000's require an HBA), then you need to remove the last DS14 prior to the CFT project.  That may involve moving root vols onto an aggr you can bring over.  

[a_jasewicz]

Thank you so much for that answer. It seems that you are stating it will work as long as I follow the cabling guidelines. My assumption is that when the drives are connected, powered on and you get to the import Data and configuration step, cDOT does not really care which ports are used as long as it is cabled correctly.

I see it as two choices

1. Get to the point where the 7 mode system is halted and  powered off the shelves. Power down the cDOT system re-rack, then power up the cDOT wait for it to become fully on-line then proceed with attaching the 7-mode disks in the new physical configuration
2. Power down the cDOT system, leave the 7mode running. Re-stack the cDOT disks where I want them , power on and then start the 7mtt process

1 would be easier than 2.  Do you see a prefference? Rather than cabling everything while all is powered off? Does it make a difference?

[SeanHatfield · Accepted solution]

It sounds like the end state is the same, and you are re-racking the cDOT system either way, so whichever is easier in your situation.  If it were me, and it were possible from a logistics/change management perspective to do the rack/stack work in advance of the CFT project I would probably do so.

[a_jasewicz]

Hi just to close. the plan to re-rack and stabilize was the correct course of action. By the time this was done there was 1/2 hour left int he maintenance window and the management team would not extend it to do the CFT. So I am back to doing the CBT over the 6 to 8 weekends and individually negotiating with application and data owners. Thank you for taking the time to answer my question it was very helpful.