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Re: Sync two disks and hot swap

On Thu, Nov 09, 2017 at 10:13:17AM +0100, Dominik George wrote:
what is the goal in having an identical copy of the disk?

It's not even so much that.

It's that the person who will be changing the disks will be hardly
capable of just that, and will not get anything close to root access to
the machine.

And I am afraid that all that complexity around automounting the
different filesystems, autounmounting, and automatically ensuring the
filesystem is clean and unmounted at the time the disk is to be swapped
could be quite unreliable.

Honestly, it's an easier problem than ensuring that a raid element is cleanly unmounted. Historically there have been external drives with buttons that could be mapped to events (but I have no idea what's on the market right now that might have an addressable button). Otherwise maybe allow the user to run "eject /whatever" with sudo, or wrap that in a single-function console login or somesuch. Another possibility is to wrap the rsync functionality in a mount/unmount cycle, so that the disk is always unmounted and ready to go except when actively transferring data.

Mike Stone