Duplicating file system

Polytropon freebsd at edvax.de
Thu Feb 21 02:21:40 UTC 2019

On Wed, 20 Feb 2019 15:02:07 -0700, @lbutlr wrote:
> On 20 Feb 2019, at 13:26, Christos Chatzaras <chris at cretaforce.gr> wrote:
> > On 20 Feb 2019, at 22:13, Christos Chatzaras <chris at cretaforce.gr> wrote:
> >> On 20 Feb 2019, at 21:52, Cerebus <kreme at kreme.com> wrote:
> >>> I have an 11.2 system with two identical SSD drives. Currently I am
> >>> using rsnapshot to keep backups of the primary drive on the secondary
> >>> drive, but I am interested in having the second drive have a duplicate
> >>> copy of the entire file system in a bootable form, updated as the
> >>> root drive is modified.
> >>> 
> >>> How would I do this?
> >>> 
> >>> I don’t really want a RAID0 because I want to also keep the periodic
> >>> backups from rsnapshot as the drives are about 10x larger than my data.
> >>> 
> >>> -- 
> >>> This is my signature. There are many like it, but this one is mine.
> >> 
> >> If both disks have the same size the easiest but not fastest way is to
> >>> use dd:
> >> 
> >> dd if=/dev/ada0 of=/dev/ada1 bs=64k
> > 
> > I read again your message and I see that you want to keep the snapshots
> > in 2nd drive, so instead of using dd you can:
> What I want is to copy all of dis1 to disk 2, bootable, but then for disk
> 2 to stay updated as new data is written to disk 1.
> So, if a log file updates on disk 1, it is updated on disk 2, if not
> instantly, very soon.

This is a typical task for a mirroring construct, but you can achieve
the same on an automated basis, either using rsync, or cpdup with the
appropriate options (only copy what has been changed, reflecting any
deletions on the source to the target).

With this in mind, I'd start with an 1:1 copy using dd, and from that
point on, have a scheduled job of rsync or cpdup in place to have any
source changes affect the "copy drive".

Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...

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