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Re: Sync two disks and hot swap

On 11/09/17 14:46, Bob Weber wrote:
On 11/9/17 2:01 AM, David Christensen wrote:
Okay.  What RAID technology were you using -- LVM, mdadm, btrfs, ZFS, other?

I use software raid with mdadm.  Its pretty forgiving with powering down and
removing a drive (after sync) and growing the array back down to the original
size.  I mainly do this on my backup server running backuppc.  The files are
compressed and hard linked between backups if they have not changed.  This makes
any other type of offsite backup pretty hard ... rsync just ran out of memory.
So adding a drive to the raid 1 and syncing is easy in comparison.  Having grub
make the drive bootable  (since the os is also on a raid 1 partition) makes the
drive very easy to just install in new hardware and get going again (assuming
the original backup system was destroyed).

Yes, rsync's --link-dest=DIR option gets tedious very quickly when you have trees of directories. (Driving rsync using scripts can solve this; perhaps this was a motivator for BackupPC?)

If your array file system is ext2, ext3, or ext4, how about unmounting the array, unmounting the destination partition, and using dump(8) and restore(8)?