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Is fabric metro cluster require all 4 mailbox disks to load ONTAP?

Is fabric metro cluster require all 4 mailbox disks to load ONTAP?

Will only local aggr mailbox disks (2) sufficient for a single node?

Is ISL link mandatory for a fabric metro cluster?

In case of force takeover mode, shutdown, startup of surviving node possible without any issues?

Re: Is fabric metro cluster require all 4 mailbox disks to load ONTAP?

Is fabric metro cluster require all 4 mailbox disks to load ONTAP?

no

Will only local aggr mailbox disks (2) sufficient for a single node?

yes

Is ISL link mandatory for a fabric metro cluster?

no

In case of force takeover mode, shutdown, startup of surviving node possible without any issues?

yes

btw, you can always kill/reset mailbox with mailbox destroy local/partner in maintenance mode.

Re: Is fabric metro cluster require all 4 mailbox disks to load ONTAP?

Hello Thomas

Thanks for response, could you direct me to a link or document in support of above if any?

You  mean ISL link is not mandatory (in absence of active connection) while booting a node.

In case of CFOD, surviving node was also made to shutdown, and while booting it definitely does not found 2 remote node disks ( in absence of ISL link, both fabrics). By releasing local/remote mailbox disks node comes up without issue? by executing destroy of mailbox disks takeover status might be lost and node comes up as takeover or stand alone (cf disable mode)?

Regards

Kiran

Re: Is fabric metro cluster require all 4 mailbox disks to load ONTAP?

Hello,

hope this help:

mailbox disks are used to determine partner status. If the mailbox status is uncertain, cf will be disabled.

Mailbox doesent affect how ontap is loaded during boot.

Lets put it this way.
In a HA configuration nodes has to know partner status.

If the interconnect link is down, filers can still see that the partner is alive because nodes can update the mailbox disks.

ISL link is used for data traffic and also to sync NVRAM (interconnect).

If you have TI zone, then you have dedicated fiber for interconnect traffic.
You cannot have fabric metrocluster without ISL link.

Force takeover is different than basic takeover in a HA.

Fore takeover is only available in metroclusters.

"normal" takeover happens when nodeA goes down, nodeB sees that, and takes the role of nodeA to side of B to serve data.

Force takeover doesent happen automatically, you have to type the command to do it.

Scenario:

ISL link breaks between the sites.

Both nodes are okay, but the mirroring for data and cf can't happen any more, because nvmem is not in sync, pool 1 (mirrrored data) is unvailable, mailbox are unavailable.

In this case, if you do a force takeover in nodeA, it will start serving nodeB data from nodeA site (mirrored data, so this is possible).

This is not what you want, because nodeB is okay, and serving data all the time.

Then you have "two nodeBs" available for the clients.

You do force takeover only when you know, that other site is down, or if you know its going to be down.

Example, air condition is broken and the heat is getting higher. you shut down the site B to avoid overheating, do the force takeover and start serve data from the site A.

Br.

Ismo.

Re: Is fabric metro cluster require all 4 mailbox disks to load ONTAP?

i doubt that this rare case occurence is documented properly somewhere :/ my knowledge comes from real life experience of getting up almost dead metroclusters ;-)

isl definately isnt needed, cf will just be disabled since partner not found.about the missing heartbeat disks, i doubt it Refrains a node from booting, could give it a go in the lab next monday.

Re: Is fabric metro cluster require all 4 mailbox disks to load ONTAP?

Hello Ismo & Thomas
I am looking at peculiar scenario where I am forcing entire fabric metro cluster to shutdown for both sites maintenance on same day/time. In entire scenario if DWDM link was not active and ISL was not available to nodes (both fabrics).

1. I can execute cf disable and bring down both nodes separately

2. In case of ISL (DWDM) link is not active,  can I bring up a single node (cf disable state)?

3. If manually disable ISL ports on switches and proceed to execute CFOD (cf forcetakover -d), shutdown of first site, next shutdown of surviving node

     upon maintenance if I try to bring the 2nd node (in absence of active ISL link) will node come up? if it,  what are the steps (like release MB disks of local/partner or any more steps to perform to bring back the node)

4. I see KB article  on mail box disks (if node not accessible need to reset mb disks) but not sure whether node comes up with only 2 local mb disks.

Thanks in advance

Kiran

Re: Is fabric metro cluster require all 4 mailbox disks to load ONTAP?

1) yes

2) in case isl goes down, cf gets disabled automaticaly

3) the Moment you disable isl, cf forcetakeover -d on one node and have the 2nd node still running, you have a split brain. dont do so

if you Need to do maintenance on node 2, do a normal cf takeover first, then disable isl and shut down node 2

4) it will

Re: Is fabric metro cluster require all 4 mailbox disks to load ONTAP?

Hello Thomas,

I want to do maintenance of both sites (metro cluster) on same day and time.

Hence I have to shutdown both nodes, once maintenance is complete I have to bring up both nodes. In case of ISL link is failed completely how to proceed?

In above node 1 takeover node2 and node 1 (takeover)/ surviving site, I want to shutdown the surviving node also. When I start node1 (which was in takeover mode before shutdown) will it comes up normally?

If any issue it encounter how to tackle the situation to bring up at least one node (either in cluster or cluster disabled state)

I will be eagerly waiting for results of testing in next week.

Regards

Kiran

Re: Is fabric metro cluster require all 4 mailbox disks to load ONTAP?

kiran,

you want to have maintenance on both nodes at the same time?

1) isl UP, on both nodes:

cf disable

halt -t 0

2) isl DOWN, on both nodes:

cf disable

halt -t 0

thats it, no need to takeover if you dont run any services on any of the sides anyway.

after maintenance is done

1) isl UP

just boot both nodes

cf enable

2) isl DOWN

just boot both nodes

cf enable will fail as the isl is down

Re: Is fabric metro cluster require all 4 mailbox disks to load ONTAP?

Will only local aggr mailbox disks (2) sufficient for a single node?

yes

This probably needs some clarification. In MetroCluster there are normally 8 mailboxes (2 on each plex of mirrored aggregate on each controller). So do you mean 2 local and 4 remote mailboxes are sufficient? Or that half of all mailboxes is sufficient?