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Re: Snapshots in tmpfs

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

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