Re: OT - 2 of 4 drives in a Raid10 array failed - Any chance of recovery?

-----Original Message-----
From: Greg Smith [mailto:gsmith(at)gregsmith(dot)com]
On Wed, 21 Oct 2009, Scott Marlowe wrote:

>> Actually, later models of linux have a direct RAID-10 level built in.
>> I haven't used it. Not sure how it would look in /proc/mdstat either.

>I think I actively block memory of that because the UI on it is so cryptic
>and it's been historically much more buggy than the simpler RAID0/RAID1
>implementaions. But you're right that it's completely possible Ow used
>it. Would explain not being able to figure out what's going on too.

You're right, the newer linux all support raid10 by default and do not do
the funky Raid1 first then raid0 stuffs combined.

>There's a good example of what the result looks like with failed drives in
>one of the many bug reports related to that feature at
>https://bugs.launchpad.net/ubuntu/intrepid/+source/linux/+bug/285156 and I
>liked the discussion of some of the details here at
>http://robbat2.livejournal.com/231207.html

I actually stumbled onto that (the 2nd link) and tried some of the methods,
but it's actually kinda of outdated I think.

> The other hint I forgot to mention is that you should try:

> mdadm --examine /dev/XXX

> For each of the drives that still works, to help figure out where they fit

> into the larger array. That and --detail are what I find myself using
> instead of /proc/mdstat , which provides an awful interface IMHO.

That's one of the problem, I'm not exactly sure.

Sda1 = 1
Sdb1 = 2
Sdc1 = 3
Sdd1 = 4

If they are following the sequence, and I'm losing sda1 and sdd1, I
theoretically is supposed to be able to recover them, but I'm not getting
much luck.

FYI.. I've left the box as it is for now and have yet to connect it back up
and all, hence, I can't really post the outputs of /proc/mdstat and
--examine.

But I will once I boot it up.

--
* Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD