Hi guys,
thanks for trying to help.
Here's the whole story: The two 1 TB disks originally were in a Synology NAS unit, not configured (to my knowledge) as any kind of RAID. The second disk was only physically installed in the NAS after the first one had been filling up. The NAS GUI showed the disks as two separate volume groups, vg1 and vg1000. I wanted to upgrade the disks to bigger size, so I took them out of the NAS and connected them directly to my Linux PC (using a USB docking station), wanting to copy the data to a couple of new disks installed in the NAS. I then went through a very steep (and incomplete) learning curve about mdadm and lvm and finally managed to mount the volumes. I could see and read all my files and stuff.
Because I wasn't yet ready to initiate the big data transfer, I unmounted the LVM disks, stopped the md stuff, and turned off the computer. When I turned it back on, I couldn't get the LVM working again. All that happens is that a tiny device "/dev/vg1/syno_vg_reserved_area" is created.
From my first trial I remember that when I read data from one of the volumes, only the corresponding LED from one drive of the USB dock flashed, from which I conclude that I definetely don't have any kind of "real" RAID on those disks. Note however the output of vgchange (below) which mentions something about a degraded RAID.
I tried re-installing the disks into the NAS. One of the disks is now reported as "Crashed", and nothing is mounted. As far as I can see all LVM metadata is intact on the disks. I also think that the data must be largely intact because so far I only did reading operations on the disks (but didn't mount them read-only the first time round).
Fortunately the data on the disks is not really essential, but a huge amount of work archiving a large CD and DVD collection... is there any way to rescure this stuff?
Here's what I tried on the Linux box so far:
root@dotcom:/home/dh# mdadm --assemble --scan
mdadm: /dev/md/3 has been started with 1 drive.
mdadm: /dev/md/2 has been started with 1 drive.
root@dotcom:/home/dh# lvmdiskscan
/dev/loop0 [ 213.51 MiB]
/dev/loop1 [ 208.05 MiB]
/dev/sda1 [ 30.00 GiB]
/dev/loop2 [ 220.89 MiB]
/dev/md2 [ 926.91 GiB] LVM physical volume
/dev/loop3 [ 206.55 MiB]
/dev/md3 [ 926.91 GiB] LVM physical volume
/dev/sda5 [ 2.00 GiB]
/dev/sda6 [ 30.00 GiB]
/dev/sda7 [ 200.00 GiB]
/dev/sda8 [ 203.76 GiB]
/dev/sdb1 [ 465.76 GiB]
/dev/sdc1 [ 149.05 GiB]
/dev/sdd1 [ 2.37 GiB]
/dev/sdd2 [ 2.00 GiB]
/dev/sde1 [ 2.37 GiB]
/dev/sde2 [ 2.00 GiB]
0 disks
15 partitions
0 LVM physical volume whole disks
2 LVM physical volumes
root@dotcom:/home/dh# vgdisplay
--- Volume group ---
VG Name vg1000
System ID
Format lvm2
Metadata Areas 1
Metadata Sequence No 3
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 0
Open LV 0
Max PV 0
Cur PV 1
Act PV 1
VG Size 926.90 GiB
PE Size 4.00 MiB
Total PE 237287
Alloc PE / Size 0 / 0
Free PE / Size 237287 / 926.90 GiB
VG UUID 9PQXmK-0dqN-3I11-1CbR-3ND3-okUD-WcySR3
--- Volume group ---
VG Name vg1
System ID
Format lvm2
Metadata Areas 1
Metadata Sequence No 6
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 1
Open LV 0
Max PV 0
Cur PV 1
Act PV 1
VG Size 926.91 GiB
PE Size 4.00 MiB
Total PE 237290
Alloc PE / Size 3 / 12.00 MiB
Free PE / Size 237287 / 926.90 GiB
VG UUID srS6Ku-i7PP-9xoZ-6kFf-IWiG-Uu9J-DcicaM
root@dotcom:~# vgchange -v -ay vg1000
DEGRADED MODE. Incomplete RAID LVs will be processed.
Using volume group(s) on command line
Finding volume group "vg1000"
0 logical volume(s) in volume group "vg1000" now active
root@dotcom:~# vgchange -v -ay vg1
DEGRADED MODE. Incomplete RAID LVs will be processed.
Using volume group(s) on command line
Finding volume group "vg1"
Activating logical volume "syno_vg_reserved_area".
activation/volume_list configuration setting not defined: Checking only host tags for vg1/syno_vg_reserved_area
Creating vg1-syno_vg_reserved_area
Loading vg1-syno_vg_reserved_area table (254:0)
Resuming vg1-syno_vg_reserved_area (254:0)
Activated 1 logical volumes in volume group vg1
1 logical volume(s) in volume group "vg1" now active
root@dotcom:~# lvdisplay
--- Logical volume ---
LV Path /dev/vg1/syno_vg_reserved_area
LV Name syno_vg_reserved_area
VG Name vg1
LV UUID ZvVm6T-FDWz-zaF4-7M4P-20i5-gXyB-4M56Hj
LV Write Access read/write
LV Creation host, time ,
LV Status available
# open 0
LV Size 12.00 MiB
Current LE 3
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 254:0
root@dotcom:~# vgs
VG #PV #LV #SN Attr VSize VFree
vg1 1 1 0 wz--n- 926.91g 926.90g
vg1000 1 0 0 wz--n- 926.90g 926.90g