Hi All,
I have an interesting question that may or may not be answerable from
some internal
ZFS semantics.
I have a Sun Messaging Server which has 5 ZFS based email stores. The
Sun Messaging server
uses hard links to link identical messages together. Messages are stored
in standard SMTP
MIME format so the binary attachments are included in the message ASCII.
Each individual
message is stored in a separate file.
So as an example if a user sends a email with a 2MB attachment to the
staff mailing list and there
is 3 staff stores with 500 users on each, it will generate a space
usage like :
/store1 = 1 x 2MB + 499 x 1KB
/store2 = 1 x 2MB + 499 x 1KB
/store3 = 1 x 2MB + 499 x 1KB
So total storage used is around ~7.5MB due to the hard linking taking
place on each store.
If hard linking capability had been turned off, this same message would
have used 1500 x 2MB =3GB
worth of storage.
My question is there any simple ways of determining the space savings on
each of the stores from
the usage of hard links? The reason I ask is that our educational
institute wishes to migrate these stores
to M$ Exchange 2010 which doesn't do message single instancing. I need
to try and project what the storage
requirement will be on the new target environment.
If anyone has any ideas be it ZFS based or any useful scripts that could
help here, I am all ears.
I may post this to Sun Managers as well to see if anyone there might
have any ideas on this as well.
Regards,
Scott.
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