Hi,

I have to failed drives that I want to give away for recycling purposes, but
want to be sure to properly clear them first.  They used be part of a btrfs
RAID10 array, but needed to be replaced (with "btrfs replace").  (In the
meantime I converted the array to RAID1 with only two drives.)

My question is how precisely the disks should be cleared.  From various sources
I know that overwriting them with random data a few times is enough to render
old versions of data unreadable.  I'm guessing 3 times ought to be enough, but
maybe even that small amount is overly paranoid these days?

As to the actual command, I would suspect something like "dd if=/dev/urandom
of=/dev/sdx bs=4096" should suffice, and according to
https://wiki.archlinux.org/index.php/Random_number_generation#.2Fdev.2Furandom,
/dev/urandom ought to be random enough for this task.  Or are cat/cp that much
faster?

Any thoughts?

Greetings
-- 
Marc Joliet
--
"People who think they know everything really annoy those of us who know we
don't" - Bjarne Stroustrup