On 19-Dec-09, at 11:34 AM, Colin Raven wrote:
...
Wait...whoah, hold on.
If snapshots reside within the confines of the pool, are you saying
that dedup will also count what's contained inside the snapshots?
Snapshots themselves are only references, so yes.
I'm not sure why, but that thought is vaguely disturbing on some
level.
Then again (not sure how gurus feel on this point) but I have this
probably naive and foolish belief that snapshots (mostly) oughtta
reside on a separate physical box/disk_array...
That is not possible, except in the case of a mirror, where one side
is recoverable separately. You seem to be confusing "snapshots" with
"backup".
"someplace else" anyway. I say "mostly" because I s'pose keeping 15
minute snapshots on board is perfectly OK - and in fact handy.
Hourly...ummm, maybe the same - but Daily/Monthly should reside
"elsewhere".
When we are children, we are told that sharing is good. In the
case or references, sharing is usually good, but if there is a huge
amount of sharing, then it can take longer to delete a set of files
since the mutual references create a "hot spot" which must be
updated sequentially.
Y'know, that is a GREAT point. Taking this one step further then -
does that also imply that there's one "hot spot" physically on a
disk that keeps getting read/written to?
if so then your point has even greater merit for more
reasons...disk wear for starters,
That is not a problem. Disks don't "wear" - it is a non-contact medium.
--Toby
and other stuff too, no doubt.
Files are usually created slowly so we don't notice much impact
from this sharing, but we expect (hope) that files will be deleted
almost instantaneously.
Indeed, that's is completely logical. Also, something most of us
don't spend time thinking about.
...
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