crush == next gen consistent hashing?

Steve Yen steve.yen at
Thu Apr 17 02:42:54 UTC 2008

Hi, first post to the list for me...

Have any folks here considered using the crush mapping algorithm with
memcached, for replication?

It originally comes from the ceph storage project, and it seems like a
nice step forward over consistent hashing.  The crush alg takes input
of a key and a weighted server node hierarchy, instead of a flat
server list,  The node hierarchy lets crush more closely match
physical server reality, representing shelves, racks, rows, etc.  For
example, you can say "Put replicas onto different shelves than the

I'm considering implementing parts of it into libmemcached with some
other ideas, but love to hear from the y'all for any wisdom/warnings.

ps, nice meeting folks at the hackathon.  Was hoping to mention this
there, but folks looked too productive on the
binary-protocol/multi-engine work and then too tired afterwards.

-- steve

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