Filesystem format for external hard disk

[Bryn M. Reeves]

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On 05/31/2012 02:35 PM, Jeff Gipson wrote:
> On Thu, May 31, 2012 at 12:15:58PM +0100, Paul Smith wrote:
>> Dear All,
>> 
>> I have got a new external hard disk, which I would like to use as
>> a mirror of my home directory (for backup purpose). What format
>> for the external disk filesystem do you recommend? And what the
>> proper command to accomplish the formatting?
>> 
> 
> ### End of Message from Paul Smith ###
> 
> For best advice, more information would be helpful... For example, 
> what's your retention policy?  If you only need a single backup,
> and not historical backups *and* you are using LVM, you might
> consider just storing LVM snaphots on the backup drive. If you want
> a more flexible solution, you might try using rsync. Tar and dump
> are also still used.

That would mean you would need to add the external disk to the system
VG (in order to be able to snapshot logical volumes from the system).

Generally that's a bad idea: if you're spreading VGs over multiple
devices, especially with snapshotting, you typically want redundancy
below the VG (i.e. mirrored or RAIDed PVs). You could also use LVM
mirroring but then you're adding more complexity to the configuration.

Things can also get ugly here if the backup disk is not going to be
present at all times (for one thing if you do ever add one to your
system VG you'll probably need to update the initramfs to ensure it
contains the required modules for the external device).

> As far as your specific question, you need the name of the device,
> and I recommend creating a UDEV rule so that every time you plug in
> the external hard drivei, the partition you backup to gets the SAME
> link in /dev. This can save you from accidentally backing up to a
> thumbdrive that was also in the USB port, or maybe a different hard
> drive. Let's

You can also just set a label on it - udisks and the modern desktop
environments will then mount it under the media directory with a name
based on the label and this will propagate to other systems you may
use the device on without the need to copy rules files around the place.

Regards,
Bryn.
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