Where is the data in ReadyDR Jobs?

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Sandshark wrote:

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The big advantages of ReadyDR seem to be synchronization of snapshots between the sending and receiving NAS and it's inherent versioning.  

 

But the inability to simply put the backup NAS into service in place of the primary if the primary goes down was a big negative for me, much more so than any advantages of ReadyDR.

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That was my assessment too.  I also use rsync with snapshots enabled on the source and destination.

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Sandshark wrote:
It may have some space saving advantages as well, but I couldn't identify any in my use case.  It probably depends on how much churn there is in your data.

ReadyDR is built on top of btrfs send, which will only send the blocks that were modified since the last backup.  Incremental rsync backup jobs will only send the files that were modified since the last backup.

So ReadyDR can be more efficient - and that will be significant will be if you are backing up iSCSI LUNS or live databases.  Rsync will need to copy the entire LUN or the entire database file every time it is updated.  I don't have LUNS or live databases on my NAS, but if I did I'd likely back them up with ReadyDR.

Since ReadyDR is backing up snapshots, the backup is always coherent (the source isn't changing while the backup is being made).  If rsync is running on the source machine, then it is also coherent - the system will make a snapshot, and then back that snapshot up.  If rsync is running on the destination machine, the backup is not coherent (so you need to run it off-hours if you need that).

Another benefit of ReadyDR is that you can run multiple ReadyDR backups in parallel (normal backup jobs are queued, and run sequentially).

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JasonBMechDev wrote:

Instead of constantly moving data from NAS1 to NAS2, NAS3, and NAS4, where each machine would use resources to receive and then snapshot the data themselves, we simply use ReadyDR Jobs to move the snapshots from NAS1 to all other NAS machines. 

 

In my experience, the resouces needed to create a snapshot are inconsequential.

Either way, the receiving machines are using resources to receive the data.  It is possible that ReadyDR can determine which blocks need to be sent more efficiently than incremental Rsync can.  That's not something I looked at in my own (fairly brief) test of ReadyDR.  I run daily backups, which complete fairly quickly - and the receiving NAS are dedicated to backup, so their resource use isn't a concern. 

The time it would take to bring a backup system online definitely was a concern for me.  You might want to try doing that on one of your backups, so you know the full procedure, and so you can set appropriate expectations.