RN202 backup / snapshots

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2ndNAS wrote:

The DUO does not support snapshots, but given that snapshot pointers are kept in folders:
Are snapshots also copied to the DUO (un-usable on the DUO), so a restore also restore the snapshots?

The shouldn't be copied. If you make snapshots accessible in the UI, some backup methods might copy them (not sure).

It would be very bad if it did. If you had a 500 GB folder with 20 snapshots, you'd need 10 TB of space to back them up. The CoW efficiency wouldn't be preserved.

So it's not practical to back up snapshots on the duo.  If you did incremental backups to another OS 6 NAS, you'd get new snapshots on the backup NAS, which is probably close enough to what you want if you do the backups often enough.  Even with another OS6 NAS you can't back up the original snapshots.

If not, I might drop RAID 1 and choose 2 separate drives in RN202, use the first disk as the Primary disk
and the second disk for manually backups of the Primary disk.

I suppose I need a backup procedure (that supports snapshots) in the rn202 for this?

 

You could do this, though  I am thinking it is less desirable than RAID-1.  RAID-1 provides redundancy for the full share (including all the original snapshots).  If you did weekly incremental backups,  then anything that is replaced on the backup drive in each backup ends up in a snapshot on the second drive.   If you change something twice during the week, then the intermediate version never ends up on the backup device.

That's because there is no way to back up the original snapshots efficiently - the best you can do is create new ones.

So I'd stick with RAID-1 on the RN202.

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Some of my files are photos, and they contain (in the internal EXIF info) the timestamp when the photo was taken.
If you adjust the colors (that is, update the photo) and save the result, the file timestamp may be set to the original timestamp.
Will OS6 detect, that the photos are updated and keep a snapshot of the original?

The primary storage on the OS6 system will work properly (the unadjusted copy remains in the snapshot).  That's because the writing of the updated file's data blocks is what unlinks the snapshot version from the updated one (CoW - copy on write).

But if the file is the same size, and has the same metadata, then an incremental backup might not detect the change, so it is possible it won't get backed up.  I'd suggest using rsync for backup (and also try adjusting the colors on a test file, and see if the backup detects it).  I think it will (it seems to me that the photo's modification timestamp will be updated, so the metadata won't be unchanged).