XigmaNAS

I have a good working ZFS with several datasets (=Datensätze in german) and one volume (=Datenträger).

At the moment the volume is also a iSCSI-target which then is used from a W2008R2 as a B2D-target.

It works, but the backup jobs fail in some cases, which seems to e caused by the sector size (=4096).
Backing up to a network share otherwise works good.

Q1 - Can I give the existing zvol a network share ? The alternative would be to destroy the zvolume an create a dataset. But I don't want to lose my existing backups.

Q2- Can I change the sector size of the zvol ?

Thank you

It isn't possible to change the sector size of a ZVol. It is always 512 bytes.

Does the iSCSI configuration have a 4096-byte sector setting? If not, the problem is probably somewhere else.

I am not sure what the reason really is.

The B2D-problems come when backing up virtual machines. But the problem seems to be only on ONE fo the VMs, the other VMs can be backed up succesfully.

the tool fsutil (on the backup-server) indeed reports 4096 bytes sector size for the B2D-volume (which is the iSCSI-target) and 512 bytes for the system drive. The failing VM also reports 512 bytes fro its system volume.

One of my first attempts to solve this problem was to change the sector size setting fro the iSCSI-target form 4096 to 512 bytes - but no change on the backup server. Even disconneting/reconnecting the target did not change anything.
fsutil always reposrt 4096 bytes sector size.
Is there something else I can do on the iSCSI-target ?

Changing the iSCSI sector size will destroy the data on it. So if that is the real problem, it can't be done. Does your VM OS or backup software have an update to handle 4096-byte sectors?

Are you sure that you aren't seeing a 4K cluster size and confusing it with sector size? How is the iSCSI formatted?