On Tue, Sep 18, 2012 at 2:02 PM, Bob Friesenhahn < bfrie...@simple.dallas.tx.us> wrote:
> On Tue, 18 Sep 2012, Erik Ableson wrote: > >> >> The bigger issue you'll run into will be data sizing as a year's worth of >> snapshot basically means that you're keeping a journal of every single >> write that's occurred over the year. If you are running >> > > The above is not a correct statement. The snapshot only preserves the > file-level differences between the points in time. A snapshot does not > preserve "every single write". Zfs does not even send every single write > to underlying disk. In some usage models, the same file may be re-written > 100 times between snapshots, or might not ever appear in any snapshot. > > > Depending on how frequently you're taking snapshots, your change rate, and how long you keep the snapshots around, it may very well be true. It's not universally true, but it's also no universally false. --Tim
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