Re: data, metadata, backup, and archive integrity and correction

On 10/1/22 09:34, Kevin P. Neal wrote:
> 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.


https://en.wikipedia.org/wiki/TIFF#Compression


If your TIFF files are uncompressed, then ZFS compression would help.


The other two choices appear to use lossless compression (?), so ZFS 
compression would not help:

* CCITT Group 3 1-Dimensional Modified Huffman RLE lossless?

* PackBits compression


(I do appreciate the advantages of uncompressed, or lossless compressed, 
photographs, audio, video, etc..)


David