On Fri, Jul 27, 2001 at 10:23:44PM +0100, Alan Cox wrote:
You dont want r/w snapshots for archiving. An archive of a
previous date is worthless if it can't be absolutely utterly and
definitively read only.
sure, for archiving you don't, but for other purposes you might
RO is easier and what most people want, this is all WAFL gives right now
RW has it's uses too, especially if you can clone /foo/bar to
/foo/blem and such like, a cheaper more elegant way of cp -Rupdl I
guess
It is hard to do well, but its an important item. One possiiblity
is to do it by replaying the log to a r/w snapshot (in ram) over a
r/o snapshot (on stable media)
you can probably get away without the need for replay... just build
and in-memory extent list of blocks to would otherwise have been
rewritten and the journal offsets, before you read a block, you check
to see if you need to get from journal first
obviously you need to make sure you get the last insatce of each block
in the journal should there be more than one
--cw
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This archive was generated by hypermail 2b29 : Tue Jul 31 2001 - 21:00:35 EST