On Tue, Aug 4, 2015 at 6:38 PM, Alex <mysqlstudent(a)gmail.com> wrote:
I panicked a bit, and didn't want to do something stupid (like
mdadm
-C) before passing it by at least one other person.
I definitely suggest you make a backup of each device superblock and
distribute it somewhere safe in the unlikely event two devices in a
mirrored array stop cooperating. The superblocks do come in handy from
time to time when they can't be acquired once problems happen.
The other thing is, if you're panicked, it kinda suggests no recent
backup. I can't tell you how many sad panda faces I see on many lists,
including the linux-raid@ list (all things RAID on Linux but mainly
md/mdadm) and it's like, really no backup? The brutal response is, if
you don't have a backup the data isn't important.
After connecting
the power cable, I was able to easily "mdadm --add" the drives back
and rebuild both degraded arrays. The /var/backup partition came up
automatically.
Great!
Another great mdadm command to know is --details.
Yeah it's easy to get -D and -E confused. -D is pointed at the running
array and -E is pointed at devices. But they're functional
equivalents.
--
Chris Murphy