2016-01-05 10:09 AM
Potential newbie question, however I've not yet found a clear answer via other channels..
In a nutshell, what's the difference between vFiler DR and Data Motion for vFiler? This is for 7-mode. Many thanks in advance..
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2016-01-05 12:30 PM
vfiler dr keeps a disaster recovery vfiler that can be activated.. Data Motion for vFiler is run from OnCommand Unified Manager and migrates the vFiler to a new target controller taking the source offline...similar to vfiler migrate, but a guaranteed migrate that completes in 120 seconds or stops the migration to retry again. There are restrictions on what is supported for data motion for vfilers but it is really nice... vfiler migrate works similarly except it will run until completion regardless of how long it takes (often less than 120 seconds but no guarantee).
2016-01-06 10:03 AM
Firstly thanks for responding. I’ve since also found a lab guide that you produced..
Excellent stuff in there. And DM-for-vfiler certainly looks slick in it’s online mode.
And I think that’s where I’m struggling... Can you picture an instance where you would want to use vFilerDR in preference to DM-for-vFiler? For example, both allow cutover/rollback and synchronisation in both directions, so technically, you could use DM-for-vfiler for providing a DR capability just as effectively as using it for permanent migration.
Maybe there are constraints around DM that mean vFilerDR is sometimes a preferred option?
2016-01-06 11:28 AM - edited 2016-01-06 11:29 AM
Great question... and one we used to go back to a lot.. I have done several migrations using vfiler DR instead of vfiler migrate or data motion for vfilers...key reason is failback capability is easier. It comes down to if you can have downtime. If non-disruptive (partially disruptive..) then vfiler migrate or even better data motion for vfilers (120 seconds guaranteed) is your best option. If you have a window to disconnect and reconnect users the I really like vfiler dr also for migrations even though it was originally designed for a dr scenario it works great. Just make sure to stop the source vfiler first...and note that stopping it isn't persistent on reboots. So if the source controller reboots then that vfiler comes back...so you could destroy the vfiler and use "vfiler create -r" to recreate it as long as all the voluems are still there. They go back to vfiler0 after the vfiler is destroyed. One other nice thing on vfiler dr is the destination can be setup on to use different ips at activation..not a big deal since you can just ifconfig and update rc and hosts but still nice for automation.
Effectively all 3 methods bring the destination vfiler online the same as the source. Some more intelligence and strict checks with UM and data motion for vfilers.
2016-01-07 04:30 AM
Well, you can use vfiler-DR for migrations, altough its primary use case is DR, but you won't get any guaranteed cut-over times.
DM-for-vfiler is designed for migrations only and does not work for DR. In order to cut-over the services both vfilers need to be alive so that the DFM server can talk to them coordinating the cut-over.
Cut-over will not work if either vfiler is unavailable, which for DR would be the case.