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Re: Live Fille System Backup

On Tue, May 09, 2017 at 12:03:14PM +0000, Curt wrote:
> Because someone mentioned Btrfs and its backup "magic," I'm looking at
> the wiki, which says (amongst other things):
> https://btrfs.wiki.kernel.org/index.php/Incremental_Backup
>  Instant, Atomic COW Snapshots
>   Since the snapshots are atomic, when a snapshot is restored it appears to
>   applications as if a power loss had occurred (and the filesystem has gone back
>   to an earlier state). Thus it is possible to backup databases without stopping
>   them beforehand. 

So, basically the same as LVM snapshots, which are independent of the
type of file system that sits on the LVM logical volume.

But btrfs is an edge with more blood on it, so people are naturally
drawn to it.  It's also more complicated.  So it's *got* to be better!!!

> I don't know what an atomic cow is (maybe some poor bovine living near
> Chernobyl) but it sounds interesting.

C.O.W. in this context is usually "copy on write".

Atomic means that it's like a database transaction: the entire operation
either succeeds, or fails.  There's no half-way state.

> I wonder if Btrfs has any notable drawbacks as a file system.

Some of the blood on btrfs is starting to dry, so the blood-seekers
are all flocking to ZFS now.  It's got a whole new TIER of buzzwords
and complexity!  It's GOT to be the best!!!

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