MISSING 3 DISKS IN 5 DISK RAIDZ2

[grei]

I know someone is going to tell me I shouldn't rely on RAIDs and that I should always have a backup but I would need another NAS to use as a backup.
I have a NAS with 5 x 3TB Seagate drivesin a RAIDZ2, I know it is wrong to do this but I bought 4 drives at the same time because they gave me a good deal to buy 4.
Here is my problem, one drive failed and so it came up as DEGRADED, I replaced it with another drive and left it rebuilding over night.
The next morning I wake up to the sound of clunking hard drives, 2 more have died during the night.
So, I have lost 3 drives out of the 5 and they are not showing up in the BIOS of my NAS.
I took them out to try in my PC, still nothing showing up in BIOS.
I brought them to work for another technician to try but they are dead.

Now I know I have lost my RAIDz but is there a way to search for files on the other 2 3TB drives?
I know software to do it in Windows but I don't think it works with zfs.

Please help me if you can.

[b0ssman]

no because one file is spread across all the drives, so if you only have 2 out of the 5 drives you are missing 1/3 of the data.

[raulfg3]

Shutdown your NAS and unplug and replug your disk, revise it for Bad cable connections, If You have a bit of luck, your pool must be mounted If not first time perhaps in a second try, once You can read your files, please save it, do not try to resilver until your data are backed.

[grei]

Thanks for your replies.
I first thought that it may be the PSU not giving enough power to the 5 drives so I tried the failing disks in 2 other computers, not recognised by the BIOS. I tried another 5 drives In the NAS all 6 ports show up so it's not bad cables or PSU. I thought I'd try swapping the PCB over from a good drive but it did work either.
Now I am wondering if opening it up and swapping the disks on one disks might work, it would be difficult to do but maybe it will work.
Any other ideas??

[b0ssman]

dont open up the drives.
they need a REALLY clean atmosphere in there and the normal air contains so much dust that it will damage the heads/surface

[raulfg3]

so I tried the failing disks in 2 other computers, not recognised by the BIOS. I

Bad news, You lose your data , sorry, remember in future to have a backup of your most important files.

[hellokevin11]

To lose so many drives is very unusual unless you are very very unlucky and have all from one batch.

I would check each drive that won't mount on an external reader, something like a usb 3.0. Don't even connect it to a pc. Just power it up and see if it spins up.

You possibly had some mb failure or power sag during read.

1. Establish if the drives are indeed dead.

[ku-gew]

I know it is wrong to do this but I bought 4 drives at the same time because they gave me a good deal to buy 4.

In this case you should start running them progressively: you put the first one in the server (with low activity, even random) for 1 month, then you add a second one, then after a month a third one, and so on.
This delays the availability of the server by n-1 months, but the wear on each disk is different and they probably won't fail at the same time.
I did this with my RAID10: I made a RAID0, I used it for 4 months, then I added one disk per vdev and I got a RAID10.

[ku-gew]

dont open up the drives.
they need a REALLY clean atmosphere in there and the normal air contains so much dust that it will damage the heads/surface

Actually I saw a video on YouTube where a guy opened an HD that had the writing head stuck, then somehow placed the head back to rest, then close the HD and he was able to read the data. If it is an emergency and the goal is only backup, not extended operation, opening an hard drive is possible and is better than not trying at all.