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Forum Discussion
Freddeco
Mar 13, 2017Aspirant
Backup fails after upgrade to 6.6.1
Hi, I have been running a 2 disk 2TB mirror in xraid readynas with full backup to external hdd once a week without any issues. I have about 228GB of data and 30GB of snapshot. not a lot. Aft...
- Mar 16, 2017The point is not "how many snapshots" but "is it transferring snapshots". Did you try StephenB suggestions?
Snapshots are at block level, understand that they contain only the blocks that are different from a reference, which makes them very efficient is used space.
Traditional backups, such as what you're using, occurs at file level. It doesn't have a clue that it's a snapshot, it only considers the files it sees - the full files - the files reconstructed with the blocks in the snapshot merged with the reference(s) - the files like you would see if you were to browse the share.
If the backup tries to transfer a single snapshot, it would require the whole file size, two snapshots, twice. If you have a share with two empty snapshots and transfer the data and the snapshots, it requires THREE times the space.
In FAT, there are other limitations, like the maximum size of a file, which is much lower than the maximum file size on BTRFS. If you were to try transfer a file too big for FAT, it would fail.
Retired_Member
Mar 13, 2017If antivirus service is still enabled, please disable, reboot NAS and try again.
- FreddecoMar 13, 2017Aspirant
already disable
- StephenBMar 13, 2017Guru - Experienced User
Did you try turning off "snapshot access" on all the shares? This won't delete the snapshots, but it should ensure that you aren't backing them up.
Note that the 30 GB used for snapshots is the incremental space needed to store the snapshot. When you back up a snapshot to an external drive, it will take about the same amount of space as the original share. This adds up quickly.
- jak0lantashMar 13, 2017Mentor
StephenB wrote:Note that the 30 GB used for snapshots is the incremental space needed to store the snapshot. When you back up a snapshot to an external drive, it will take about the same amount of space as the original share. This adds up quickly.
I thought this was fixed a long time ago, is it still happening? When backing up a volume or a share to an external, it should NOT transfer the snapshot. As you said, it would duplicate the data (reconstructing the data) and explode in terms of volume. But my understanding was this behavior was changed by not transfering the snapshots when backing up to an external storage.
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