Replication Testing (Performing a Switch over)

Question

I'm reading the Using Celerra Replicator guide and it is fairly clear on how to perform a switch over from the Source to the Destination. However that is where it ends. We are wanting to test a Switchover, make sure the VDM's and File Systems come online and work and are accessible and then put it all back to the way it was. Can someone enlighten me on what to do when we want to move it back to its original SOURCE? Here are my steps thus far. Verify replication sessions (From the SOURCE Celerra) $ nas_replicate –list dev_vdm_local_replication vdm server_2 -->celABC_local cel0123 OK dev_fs_local_replication filesystem server_2 -->celABC_local cel0123 OK From the DESTINATION $ nas_replicate –list dev_vdm_local_replication vdm server_2 <--cel0123_local celABC OK dev_fs_local_replication filesystem server_2 <--cel0123_local celABC OK From the SOURCE For DEV, VDM and DEV File System switch over $ nas_replicate –switchover dev_vdm_local_replication $ nas_replicate –switchover dev_fs_local_replication At this point after DNS is updated I expect to be able to access our resources from the TARGET Celerra. After some testing, we want to move it all back to the way it was and are not concerned about replication from DESTINATION to Original Source. Please advise! Thanks!

DHoffman2 · Answer

Well, I answered my own question.... If anyone has any questions on my procedure (which was modified from what I posted) let me know.

Manumari · Answer

Hi, Just wanted to know, after a switchover, how were you able to get back to original state with out copying data to the source from distinate ? Can you put your steps in here ? Thanks,,

DHoffman2 · Answer

I had to allow replication to occur from the TARGET back to the SOURCE. This was something I was hoping not to have to do, but it makes sense if you think about it.

Because this is a controlled switch over and you want the resources to come online, (even though this was just for a test) in order to Switch BACK over, the VDMS, Replication sessions and the File Systems all have to be in a specific state.

From the Target (now the Source) started replications of the VDM and File Systems (using the GUI to perform these functions).

Once I verified the replication was from Target back to Source, I could now perform the "SWITCH OVER" again.

I did that and all was right with the world.

So, to recap,

I WANTED to perform the switch over without repicating back to the Source from the Target. Since the Target becomes the Source during the switch over, you must allow for that to occur before you can switch back.

My manager has asked for this test again, so I hope to be able to provide additional information. I dont have an ETA on when this will occur, but once it does, I will edit this with specific CLI commands.

Manumari · Answer

Thanks for the information. So is there a way we can discard the test data on the target and get back to normal setup replicating from source to target back or NOT ? thanks

DHoffman2 · Answer

In my opinion, it is not considered 'TEST' data, unless you specifically put some files/folders what have you, in a specific location and then delete them after your testing is complete. Because of the nature of the switch over, the target becomes the source until such time as you switch it back. Who knows who may be modifying a file, adding data, etc while the resources are running on a different Celerra. THe only other thing to do, would be create a TEST VDM, CIFS servers and File system and play with it that way. (in hindsight, this is what I should have done).

Manumari · Answer

Good to know. Helped a lot. Thanks very much for the input and thanks everyone as well.

umichklewis_ac7b91 · Answer

Excellent!  When you post your commands, can you ask the mods to make this a sticky/permanent entry?  It would be extremely handy. Thanks! Karl

DHoffman2 · Answer

We have performed a switch over test again and am leaving it switched over for an extended period of time.

While examining the target celerra (where the switched over VDM and FS are currently running) we noticed that when viewing the CIFS SHARES, there arent any listed in Celerra manager. Is this by design? If not, is there an issue? Can we create new shares while "switched over" and if so, can that cause any issues with the existing shares that were created while running on the source?

Dr.diSousa · Answer

Hi, this was my situation...

We are migrating a CIFS server (VDM and FS) from NAS02 to NAS03 with Celerra Replicator v2.

After follow the steps to switchover VDM and FS, we noticed that in destination (NAS03), the IP in destination did not respond to ping.

We found a problem with the Cisco Switches and VLANs..... the VDM and FS now are in a switched over state (Source is in RO and destination is in R/W). As we found a problem, we cannot continue with the migration and we have to roll back, there is no sense to reverse the replication, I'ld like to resume the replication from source (NAS02) to destination (NAS03) discarding the changes in NAS03 (there was no changes because the IP doesn't work...)

So In this way there must be a way to recover the original replication from a switched over state....

Any idea how to do it?

Manumari · Answer

I am not so sure about the VDM but for the FS, make the target FS RO and Source as RW and resume the replication discarding the changes on the target FS

dynamox · Answer

you will need to start replication in reverse order and then reverse replication nas_replicate -start repl_fs01 -reverse nas_replicate -reverse repl_fs01

julianojeziorny · Answer

Not entirely true, one can in fact restart a switched over replication without hav ing to reverse it first by making the destination volume RO first:

On destination:

server_mount server_2 -option ro FS_NAME

Then on source start the replication with overwrite_destination option

nas_replicate -start REP_NAME -overwrite_destination

Celerra

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