In reading this blog post:
http://blogs.sun.com/bobn/entry/taking_zfs_deduplication_for_a
a question came to mind.....
To understand the context of the question, consider the opening paragraph
from the above post;
Here is my test case: I have 2 directories of photos, totaling about 90MB
> each. And here's the trick - they are almost complete duplicates of each
> other. I downloaded all of the photos from the same camera on 2 different
> days. How many of you do that ? Yeah, me too.
OK, I consider myself in that category most certainly. Through just plain
'ol sloppiness I must have multiple copies of some images. Sad self
indictment...but anyway....
What happens if, once dedup is on, I (or someone else with delete rights)
open a photo management app containing that collection, and start deleting
dupes - AND - happen to delete the original that all other references are
pointing to. I know, I know, it doesn't matter - snapshots save the day -
but in this instance that's not the point because I'm trying to properly
understand the underlying dedup concept.
Logically, if you delete what everything is pointing at, all the pointers
are now null values, they are - in effect - pointing at nothing...an empty
hole.
I have the feeling the answer to this is; "no they don't, there is no spoon
("original") you're still OK". I suspect that, only because the people who
thought this up couldn't possibly have missed such an "obvious" point. The
problem I have is in trying to mentally frame this in such a way that I can
subsequently explain it, if asked to do so (which I see coming for sure).
Help in understanding this would be hugely helpful - anyone?
Regards & TIA,
-Me
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