Synchronize Destination Snapshots With Source?

[Phase]

Hi,

I deleted snapshots from the source and the replication failed with a "No incremental base on dataset and replication from scratch is not allowed" message. My understanding is that the "fix" is to check/enable "Synchronize Destination Snapshots With Source". However, I was planning on deleting snapshots periodically. The help section says "If the destination system has snapshots but they do not have any data in common with the source snapshots, destroy all destination snapshots and do a full replication. Warning: enabling this option can cause data loss or excessive data transfer if the replication is misconfigured."

So my question is, will this cause the entire dataset to be replicated (30 terabytes) or will it cause only the snapshots that were deleted on the source to be synched/deleted in the target? Running TrueNAS-12.0-U4.1 on both.

Thanks!!

 

[Phase]

Well, not quite sure what happened, but the dataset on the destination was gone... disappeared.

So I upgraded from TrueNAS-12.0-U4 to TrueNAS-12.0-U5, created the dataset on the destination, deleted the old replication task, created a new replication task and started it. It will take a while.

Bummer, not exactly belt and suspenders.

 

[Phase]

2 days running and we are halfway there! That was a very easy way to obliterate a lot of data.

I suppose the lesson is... once the replication is up, don't mess with the snapshots!!

 

[jay413]

Thanks for updating you progress on this thread. I'm in a similar position (with the error "No incremental base on dataset and replication from scratch is not allowed") after creating a new snapshot task and updating the replication task to use it. I'm worried that FULL replication will be done ... I don't want that with 91 TB of data.

 

[Phase]

After that experience, if I were to make a change, I would create a small test dataset, replicate it and try the different conditions. I'm sure there is a reason for things to work the way they do, but the mechanisms are not clear to me as an end user. I would also try to edit the snapshot rather than replace it. It seems that the replication is replicating snapshots, rather than datasets -- which kind of makes sense as datasets are in flux. BTW, I seem to recall that I changed snapshot retention periods on the source and that propagated correctly to the target -- but I could be misremembering.

Good luck!

 

[jay413]

Thanks for the response. If "It seems that the replication is replicating snapshots, rather than datasets" is true, that would be good news for me. I have no issue if only snapshots are replicated (but not the complete dataset), I just don't want to do a complete copy of the dataset again (at 91 TB). I'll take your advice and try on smaller test datasets.