Unreadable HDD in NAS542

gambrinus777

Hi all,
I've a problem with my NAS542 in which I have installed 4 HDD creating a Volume in RAID 5 as suggested from the wizard.
Now the HDD are unreadable by the NAS, the Volume disappeared and it's not possibile to read the disk.
How can I solve this?

I've also put the HDD in a usb docking station connected to a linux pc and try to use testdisk to recover my file and below you can see one of it.

I can change the type of the Partition.
Which type I have to choose to recover it?
Thanks

#NAS_Dec_2018

Mijzelf

You can't recover it by changing the type. You'll need to connect at least 3 of the 4 disks to be able to assemble the raid volume.

gambrinus777

I've followed your suggestion: two of the four disks have problems and the wizard suggest to replace them. The question is: if I replace this two disks with new one I will be able to recover all my data and the raid volume?

Mijzelf

if I replace this two disks with new one I will be able to recover all my data and the raid volume?

No. On a 4 disk raid5 volume all data is stored across 3 disks, and a 4th disk is added for parity. So you'll need 3 disks to recover your data. If both problem disks are indeed dead, your data is lost.

But it is possible that one is only dropped from the array due to a minor problem, in that case it might be possible to re-inject it to the array.

Can you put the disks back into the NAS, in the same sequence if possible, enable the ssh daemon, login as root put the result of next commands here:

<p>cat /proc/partitions</p><p>cat /proc/mdstat</p><p>mdadm --examine /dev/sd[abcd]3</p>