Readynas Ultra 4 RAID 5 - 2 of 4 disks fail at the same time

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Tomahna wrote:

Something must have gone wrong with adding the attachment. Let me try again

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Well, clearly RAIDar is confused since disk 1 isn't installed.  Did you try logging into Frontview?

Yes I looked at Frontview (see attachment for the status screen). The strange thing is that it also reports disk 1 present. While the unit knows it is not (the light for it is off). I will also attach the system log file. It shows that is tries to configure raid for 3 disks instead of 4. So I find it confusing that the status is not consistanly reported. Could there perhaps be some data corruption in de setup or in the local data of the unit itself (i.e. Not stored on the raid disks?).

And the system.log for today’s boot.

The disk numbering starts from 0, so the boot process is detecting that the first disk isn't present.  And you are getting read failures on the second disk, so the array can't be mounted.

Your Frontview screenshot shows the first two disks as not working (disk 1 of course is removed) - the SMART stats button for both is grayed out.

Clear, thank you. I suspected as much when I looked at the system.log file

What remains confusing is that frontview displays the disk specificatiions for disk 1 (only without temperature) while it is not present, but that is not a problem for me. When I check te logs for the disk_smart disk log it reported before that all 4 disks passed the tests. That is probably why RAIDar is reporting 4 (Green lights) available disks.

I will continue doing some more tests this week and determine my options. I’ll report back when I’ve reached that point. Again thank you!

It has been a while since I had time to continue working on this problem, but this week I made some progress. Unfortunately I ran into a new (seemingly unrelated) problem. I recovered the first disk by cloning it. The replacement disk resulted in the unit coming back online! Note I have not cloned the second disk, since this disk has so many bad sectors and I intented to use a new disk voor slot 2 and then want sync it.

Unfortenately - for no apparent reason - one of the healthy disks has now been marked as unusable?! As a result only some of my Shares have come back online. Others most likely depend on the presence of the other disk. Checking the system log it reports that disk 3 is non-fresh

Apr 24 11:24:17 Serenia kernel: RAID conf printout:
Apr 24 11:24:17 Serenia kernel: --- level:5 rd:4 wd:3
Apr 24 11:24:17 Serenia kernel: disk 0, o:1, dev:sda5
Apr 24 11:24:17 Serenia kernel: disk 2, o:1, dev:sdb5
Apr 24 11:24:17 Serenia kernel: disk 3, o:1, dev:sdc5
Apr 24 11:24:17 Serenia kernel: md2: detected capacity change from 0 to 5986692759552
Apr 24 11:24:17 Serenia kernel: md2: unknown partition table
Apr 24 11:24:17 Serenia kernel: md: bind<sdc6>
Apr 24 11:24:17 Serenia kernel: md: bind<sdb6>
Apr 24 11:24:17 Serenia kernel: md: kicking non-fresh sdc6 from array!
Apr 24 11:24:17 Serenia kernel: md: unbind<sdc6>
Apr 24 11:24:17 Serenia kernel: md: export_rdev(sdc6)

Perhaps in the attempts to recover the array, a shutdown was not completed properly (however I'm not aware of it), because I found the following information on a linux forum: 

This can happen after an unclean shutdown (like a power fail). Usually removing and re-adding the problem devices will correct the situation:
/sbin/mdadm /dev/md0 --fail /dev/sda5 --remove /dev/sda5
/sbin/mdadm /dev/md0 --add /dev/sda5

My question now is, what is the best way to re-activate disk 4. Should I attempt the above commands for sdc6 or should it be sdc5. Or should I go about it differently? 

PS I'm confused about the reference to sdc6, because I only see sdc5 listed as a mounted disk in the system log...