Re: Snapshots in tmpfs

[David Holland <dholland-tech%netbsd.org@localhost>]

On Wed, Feb 22, 2012 at 08:17:15AM -0600, David Young wrote:
 > On Wed, Feb 22, 2012 at 01:42:45PM +0100, Manuel Wiesinger wrote:
 > > *)
 > > What is it good for? The only practical use I can imagine are
 > > backups on thin clients, which operate without a hard disk. But this
 > > is clearly far-fetched, in my eyes.
 > 
 > It's good for writing checkpoints of a tmpfs to non-volatile (NV)
 > storage in an embedded system where writing to the NV storage is costly
 > (it wears out, or it is slow, or both).  When you have a snapshot, you
 > can stream it to NV storage using pax(1).  This is the best practical
 > way that I can think of in NetBSD at this time.

other than, say, chfs or lfs?

That sounds like a horrible hack, anyhow, and prone to dying horribly
if you crash or lose power in the middle of a writeback. (plus you'd
want to use rsync to transfer, or so I'd think, or rewriting
unmodified blocks will burn write cycles faster than not bothering to
do anything special.)

-- 
David A. Holland
dholland%netbsd.org@localhost