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From Kevin Burton <>
Subject Disabling the write ahead log with 2 data centers?
Date Fri, 23 Jan 2015 17:59:43 GMT
The WAL (and walls in general) impose a performance overhead.

If one were to just take a machine out of the cluster, permanently, when a
machine crashes, you could quickly get all the shards back up to N replicas
after a node crashes.

So realistically, running with a WAL is somewhat redundant.

ESPECIALLY when you have 2 data centers at 3 replicas in each datacenter
(for a total of 6 replicas).

I think this would only be about a 15% performance overhead.

Additionally, on flash, if you lay out the SSTables properly, you arguably
don’t need a WAL because your SSTable itself can be a wall and you could
run without memtables.   This has been proposed in a number of situations.
Especially on something like FusionIO …



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