TS-832 will not mount volume

[hfeb22]

We have a TS832 with 5 Samsung 870 QVO 4TB disks, 4 in a raid5 and one spare. Recently one disk failed and we replaced it and the raid rebuilt ok. We later checked the failed disk with a samsung utility and it had no errors. A week later one more disk failed that triggered a rebuild and then during rebuild, another disk failed also. The system is only 6 months old and Estimated Life Remaining is 100% so, for me, it looks like the disks are not compatible with the Qnap.

The error was
Warning 2022-09-18 19:38:24 System 127.0.0.1 --- --- [Bad Block Log]: Invalid data found on Host: Disk 3 at sector (3238962688, 128, 1).
and later
Warning 2022-09-18 21:55:03 System 127.0.0.1 --- --- [Bad Block Log]: Invalid data found on Host: Disk 1 at sector (2030248960, 128, 1).

The rebuild stopped. After this I tried to rebuild the raid group with disk 1, 2 and 4 and the rebuild completed, however, the volume will not mount and a Check says:

Failed to check file system for volume "DataVol1". Storage pool: 1.

lvchange -ay /dev/vg1/lv1 says "Check of pool vg1/tp1 failed (status:1). Manual repair required!"
lvconvert --repair /dev/vg1/tp1 says "Volume group "vg1" has insufficient free space (0 extents): 16384 required."

md_checker says
Welcome to MD superblock checker (v2.0) - have a nice day~

Scanning system...

RAID metadata found!
UUID: 738533e9:f9f72a1b:1221b762:28ba639b
Level: raid5
Devices: 4
Name: md1
Chunk Size: 512K
md Version: 1.0
Creation Time: Apr 4 11:54:17 2022
Status: ONLINE (md1) [UU_U]
===============================================================================================
Enclosure | Port | Block Dev Name | # | Status | Last Update Time | Events | Array State
===============================================================================================
NAS_HOST 1 /dev/sdb3 0 Active Sep 28 14:32:30 2022 261 AA.A
NAS_HOST 2 /dev/sda3 1 Active Sep 28 14:32:30 2022 261 AA.A
NAS_HOST 3 /dev/sdd3 2 Active Sep 16 17:34:26 2022 145 AAAA
NAS_HOST 4 /dev/sdc3 3 Active Sep 28 14:32:30 2022 261 AA.A
===============================================================================================


What can I do to at least get the data mounted as read only? Is there a professional Qnap support I can contact?

[dolbyman]

could be this

viewtopic.php?f=25&t=134212

a hardware defect, open a ticket with qnap if you want to contact qnap