Re: Raid5 Array stopped suddenly, no apparent error messages.

[John Robinson <john.robinson@anonymous.org.uk>]

On 09/05/2012 19:08, Brian McKee wrote:
> If this is not a good place to ask for help, please point me to where I
> can ask. Sorry if I offend.
>
> TL;DR: My question is this: is it safe to run mdadm --create
> --assume-clean on an existing array? And by safe I mean: is it
> guaranteed that the existing ext4 partition's data will not be lost when
> I run the command?

Any --create --assume-clean will only rewrite the metadata. You would 
need to get the command exactly right, specifying the chunk size, 
metadata type and member partitions in the right order in order to be 
able to see your filesystem. However...

[...]
> For more details you can read this gentoo thread:
> http://forums.gentoo.org/viewtopic-p-7033578.html
>
> Summary: The three drives won't assemble because they are not fresh.

I don't think you are seeing the recent kernel bug; you can see all the 
correct metadata on all your drives.

The problem you have is that your member partitions have different event 
counts. You can force the assembly, ignoring the different event counts, 
with --assemble --force. You should then run a fsck as there may already 
be some corruption which occurred when the event counts got out of sync.

You should also try to track down what caused the issue in the first 
place. Check your logs for ata errors.

Cheers,

John.