Date: Sat, 1 Oct 2022 12:34:11 -0400 From: "Kevin P. Neal" <kpn@neutralgood.org> To: David Christensen <dpchrist@holgerdanske.com> Cc: questions@freebsd.org Subject: Re: data, metadata, backup, and archive integrity and correction Message-ID: <YzhsAw/bUevYmBSX@neutralgood.org> In-Reply-To: <166467a7-5aac-6c67-c462-432912c58211@holgerdanske.com> References: <b027f6af-bf83-2663-b0ef-2480e385b189@holgerdanske.com> <c15361a3f8328583bdab528c5a49bf475a1dfdfa.camel@riseup.net> <7be8f47b-bfea-ef5a-7b59-2f94f8d310e2@holgerdanske.com> <ed8431a943b8d3cd74e588c7ee9901c6c166eba8.camel@riseup.net> <166467a7-5aac-6c67-c462-432912c58211@holgerdanske.com>
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On Fri, Sep 23, 2022 at 06:58:24PM -0700, David Christensen wrote: > But de-duplication and compression of other data is debatable. > Photograph files are already compressed; so ZFS compression will be Sure, if you use jpeg. If you use TIFF as your intermediate format then the compression goes away. Camera sensors are something like 12 to 14 bits of sensitivity. Using jpeg throws away that data when you might need it for your editing. TIFF preserves it because TIFF is 16 bits per channel. When you are done and are exporting a picture then jpeg is a good choice. > useless. 10 copies of the exact same photograph file should > de-duplicate nicely. But, open a photograph file in an editor, make > some changes, save as another file, and repeat 8 more times is likely to > result in 10 files all with different blocks; so ZFS de-duplication will > be useless. TIFF doesn't suffer from generation loss like jpeg or VHS either. -- Kevin P. Neal http://www.pobox.com/~kpn/ "A pig's gotta fly." - Crimson Pig
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