Error truncating file while incremental backup with btrfs and CBT client


I have UrBackup running in a NetGear NAS, which is armel architecture based (armv7l). It is running with BTRFS storage and it is working very fine from a few weeks ago. I installed UrBackup from sources into this NAS. The OS is a Debian 8 fork from NetGear.

I receive this error in two of my clients when do incremental backup:

I have seen this error a few days ago in other of my clients and it was exactly the same, also with a PST file. Then I have do some tests and finally I found that when I do a complete bakcup of this client the problem dissapears and subsecuent incremental backups works again.

But now it is happening again in other two different computers, so I think I must ask for support.
The clients are running Windows 7 Pro x64 and x86 with CBT client. Anyway I think this is a server issue.

I think the problem is in some place whit the snapshoting system. I have seen that snapshots for those failed backups are not deleted:


I think if I do a complete backup of this client It probably fix the error, but I think probably it will happen again.
¿Any idea?

Thank you so much.

It cannot resize the file during backup (system call fails). Probably a btrfs issue.

Is your pst file really that large (~23 GB)?

Yes, these files are larger than 23 GB. Is there any workaround?
Why works for some time and then it fails?
Do you think this is a problem of the btrfs implementation of this NAS?


I have seen that in the other client that is failing, the data amount is much fewer than 23 GB… I attach the error log


@uroni any help on this?
Do you think it is a BTRFS issue in this NAS? or a UrBackup issue?

FYI, I have seen also that in these clients, the post incremental batch file is running like the backup has finished correctly.

Many thanks.


Can you give any hints about any prossible solution to this problem?
As I tell in previous messages, the problem dissapears when I do a full file backup of these clients, after that, incremental backups are working again.

Thank you.

Update the linux kernel on the device to e.g. 4.14 (I know this probably won’t be possible, so you’ll have to use another fs or run UrBackup in a VM).

Ok, I will evaluate these options.

Thank you.