flattened wrote:

I was going to use a 2TB share size. The nightly full backup is (to use an easy figure) 200GB (of which in reality only 1 GB or less of data actually changes) and I was advised that I'd be lucky to get a week's worth of snapshots.

Does this ring true?

If the full backup is a single file, then rsync would rewrite the entire file - taking a fair amount of time over the network, and also shifting the previous nightly backup file to the snapshot (adding 200 GB to the snapshot space).

If the backup is large set of files, then only the files that changed are rewritten, and there is much less increase in the snapshot size. It'd be more than the 1 GB of changed data (since unchanged data in the changed files is also re-rewritten by rsync), but not the full 200 GB.

flattened wrote:

As a result I've created an iSCSI LUN of 1.5TB that the WSB will see as a dedicated device that it can indeed do incremental backups to, that I can also set to also snapshot nightly.

So, looking further, should the decision be made to get another offsite NAS for belt&braces purposes I'd use ReadyDR on this source LUN to a share on the offsite box???

ReadyDR generally works well for LUNs. Updates to blocks on the LUN on the source will increase the local snapshot size needed on the source of course. ReadyDR will migrate those changed blocks to the destination NAS efficiently.

How well this works with your software depends on how many blocks of the LUN are re-written when the WSB backup runs. If the WSB re-writes unchanged blocks, then it won't work very well. I'd try it locally first, and where you have more bandwidth to work with (and easier access to the destination machine).

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