snapshot implementation

[patpro]

On Wed, 23 Dec 2009 14:56:18 -0600, Barry Pederson <bp at barryp.org> wrote:
> "...there's virtually no overhead at all due to the copy-on-write 
> architecture. In fact, sometimes it is faster to take a snapshot rather 
> than free the blocks containing the old data!"
> 
> That's certainly not the case with UFS snapshots, which can take a long 
> time to complete (we're talking freezing your machine's disk activity 
> for many minutes), and are limited to 20 total.


UFS uses copy on write. But you say many minutes to complete? Don't you
speak about dump(1), that uses snapshot as a basis to dump a live file
system?
I agree, UFS snapshot creation is not lightning-fast, but many minutes
seems a lot to me, and I never experienced such a long creation time.

patpro