HAMMER filesystem update - design document
dillon at apollo.backplane.com
Wed Oct 10 14:30:32 PDT 2007
:Tells me: "ZFS, bend over, grab your ankles and kiss your an(atomy) 'Goodbye'"
: From the amount of work that has HAD to go into this, it also tells me you are:
:A) probably single, or soon will be and
:B) don't sleep much anyway!
I get a good 8 hours of sleep. As I get older I find myself unable to
pull all-nighters any more without really screwing up the entire next
ZFS serves a different purpose and I think it is cool, but as time
has progressed I find myself liking ZFS's design methodology less and
less, and I am very glad I decided against trying to port it. I do
not think it is a good idea to put all one's marbles in a single copy
of a filesystem, no matter how redundant its storage model is, and there
isn't much point having that level of redundancy if the intent is
to operate in a replicated environment.
The problem ZFS has is that it is TOO redundant. You just don't need
that scale of redundancy if you intend to operate in a multi-master
replicated environment because you not only have wholely independant
(logical) copies of the filesystem, they can also all be live and online
at the same time.
HAMMER's approach to redundancy is logical replication of the entire
filesystem. That is, wholely independant copies operating on different
machines in different locations.
Ultimately HAMMER's mirroring features will be used to further our
clustering goals. The major goal of this project is transparent
clustering and a major requirement for that is to have a multi-master
replicated environment. That is the role HAMMER will eventually fill.
We wont have multi-master in 2.0, but there's a good chance we will
have it by the end of next year.
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