[ Date Index ] [ Thread Index ] [ <= Previous by date / thread ] [ Next by date / thread => ]
On Tue, 9 Feb 2016, Tom wrote:
One of my backup drives has just gone dead. Going to get a pair of USB drives with the intention of somehow exposing the two as one so that I can take one away for safe keeping and then, when I plug it in it the current active one will be mirrored to it and then unmounted for taking out for safe keeping.Anyone seen any scripts around to allow me to do this with relative ease?
You can use Linux software RAID mirroring as the back-end to this. Not sure I recommend this way of keeping a backup though, however it can be done.
Build the mirrored set, put your data onto it, then soft-fail the drive you want to remove, (mdadm --fail /dev/md1 /dev/path/to/removing/drive) remove it and store it.
System carries on. Plug in the drive and re-sync the mirror with the right mdadm command e.g. mdadm --add /dev/md1 /dev/path/to/removing/drivewait for it to complete - watch -n cat /proc/mdstat then repeat the soft-fail & remove process.
You might want to use /dev/disk/by-uuid/... to make sure you're using the right device.
You can script that with a script fired off from the udev trigger when the system sees the drive.
The huge downside of that, is that every sector on the in-use disk will be read and every sector on the updating disk will be written. It takes time and you need perfect drives all the time. (There is a bitmap option to mdadm that came make this quicker, but I think it only supports ext2/3 at present)
Plan B would be to not use a mirror system but to have a separate filesystem on the removable drive and use rsync. With clever use of rsync you can store many days/weeks/months of data, depending on how much changes between backups. Again, scripts fired off from udev can do the copy. This is the way I copy my camera to my desktop - however I have a simple script, so I plug in the camera, run the script then unplug it.
I think I'd simply off-site backup via this interweb thing to a remote server in a bunker somewhere using e.g. rsync. (which is actually part of what I do) - the downside being the time to recover it should it need recovery.
Gordon -- The Mailing List for the Devon & Cornwall LUG http://mailman.dclug.org.uk/listinfo/list FAQ: http://www.dcglug.org.uk/listfaq