Block level backups don't work for local disk backup storage.
I'm testing backups on Suse linux, with the backup medium being local disks.
I find that block level backups don't appear to work.
To test I backed up a 60MB file, then modified it with vim by inserting a string of random characters. Each backup still displayed that it backed up the 60MB.
I don't know if it matters, but the backup destination filesystem is BTRFS.
I read that CBB supports block level backup to the cloud.
Can anyone confirm if block level backup work with local file systems on linux? And if so, what file systems are supported for block level backup.
First of all, I can assure you that the Block-level works. Please check that you have enabled it on the first step of the Backup Wizard.
Secondly, yes. Backup works with block-levels to the local file system, whatever the destination file system is but the thing is that we don't work with their features (yet). So if you'd ask for whether we support BTRFS snapshotting - no, we do not. We simply upload the file, and in case of block-level, the changed part with it's map (cbbitmap).
So yes, the Backup would work, but we'd recommend to have a second copy in the cloud.
I did some further testing and documented my steps here:
Backup log with comments
Going from the bottom of the list up, first to last..
The first to the third backups worked as expected.
Then I enabled compression, which resulted in a complete full file backup. I can see how this may be the case because the compressed file "looks" completely different to the original 1st uncompressed backup.
A slight file change was made, and the next block level incremental worked OK at 112.06KB
The part that I don't fully understand is that the last two test backups were "Forced full backups", just to test what would happen.
Prior to this I've read somewhere about CBB's synthetic backups. But it looks like there is no synthetic full backup on Linux, it is indeed a full file backup with no links to previous unchanged files.
If my testing is working as you expect, then is there any way CBB can efficiently deal with one particular use case I have in mind. Being DATA of approx 6TB, backing up to 8TB USB drives.
In this scenario, only one full backup will fit on a disk, though many block level incrementals could be catered for. But at some point the disk will fill, and none of the old data would be purgeable due to blocklevel chaining.
Would this scenario be better served with compression=ON and blocklevel=OFF?
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