Question about snapshots, replication, and retention

[VulcanRidr]

A quick question about snapshots and replication. I am taking snapshots on an SSD-based TrueNAS box, which is then being pushed off to a much larger spinning rust-based TrueNAS, that is being used for snapshots for all of my production datasets as well as cold storage for no-long-in-use datasets that cannot be deleted. Since the production NAS in question is SSD based, it is significantly smaller than the spinning rust ones. So it is getting tight on space...So this is my question. If I were to delete some of the oldest snapshots, would that also auto-delete the replicated snapshots, or would they stay around for the full retention period?

I am hoping the latter is true, as mgmt is not comfortable with just "losing" those older snapshots, however I am not comfortable with the usage on the dataset sitting around 90% either.

Thanks.

 

[Patrick M. Hausen]

If this is a replication task created in the UI, the destination can have its own retention policy.

 

[VulcanRidr]

Hi Patrick,

It was indeed created in the UI. (I had the admonition to "never do anything on the command line behind the gui's back" drilled into me when I started using it.) Where do you access that retention policy? Is it by default set to whateve the parent snapshot is? And can it be changed after the fact?

 

[Patrick M. Hausen]

 

[VulcanRidr]

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Ok. Thanks. Mine are set to "Same as Source" and the retention period for replicated snapshots is 8 weeks. Since I am in a bit of a space crunch on the SSD pool, I just want to make sure that that if I manually delete snapshots on the source, the remote snapshot won't go away the next replication, as I thought that I read somewhere that that was how they normally worked.

 

[Patrick M. Hausen]

It does work like that if you set "same as source". At least I think that "same as source" implies "delete all snapshots not present on the source." One would have to check the source code to be sure.

So to be safe define a custom retention policy and the system will use that.

 

[VulcanRidr]

It does work like that if you set "same as source". At least I think that "same as source" implies "delete all snapshots not present on the source." One would have to check the source code to be sure.

So to be safe define a custom retention policy and the system will use that.

Okay, thank you for that clarification. Looks like I need to change the retention policy. :)