NAS540 Volume down ...need help

Mijzelf

News from the nas. With
mdadm --create....
the nas didn´t start a recovery. The Partition sdb1..3 were los.

Recovery? The idea is to rebuild a degraded md2. If that is done, and the filesystem is OK, you can let the firmware add the 4th disk.

The whole idea of a 4 disk raid5 is that it can also run with 3 disks.

Leave sdb until you can see your data.

fdisk says, bad partition table backup at sdb and work with primary table...

The disk has a GUID partition table, which is supposed to have a 2nd copy at the end of the disk.