Unfortunately I'm not able to access the data on my NAS anymore. I can't figure out why this is the case as I haven't changed anything. So I plugged one of the harddisks in my computer to access the data. What I did:

kpartx -a /dev/sdc

Now I should be able to access

/dev/mapper/vg001-lv001

When trying to mount it I get:

sudo mount -t xfs /dev/mapper/vg001-lv001 /home/user/mnt
mount: /dev/mapper/vg001-lv001: can't read superblock

Now I did a

parted -l

which gave me

Modell: Linux device-mapper (linear) (dm)
Festplatte  /dev/mapper/vg001-lv001:  498GB
Sektorgröße (logisch/physisch): 512B/512B
Partitionstabelle: loop

Number  Begin   End    Size  Filesystem  Flags
 1      0,00B   498GB  498GB  xfs

Does anybody have a solution how to recover the data?