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From Mark Jones <>
Subject At what point does the cluster get faster than the individual nodes?
Date Wed, 21 Apr 2010 15:28:41 GMT
I'm seeing a cluster of 4 (replication factor=2) to be about as slow overall as the barely
faster than the slowest node in the group.  When I run the 4 nodes individually, I see:

For inserts:
Two nodes @ 12000/second
1 node @ 9000/second
1 node @ 7000/second

For reads:
Abysmal, less than 1000/second (not range slices, individual lookups)  Disk util @ 88+%

How many nodes are required before you see a net positive gain on inserts and reads (QUORUM
consistency on both)?
When I use my 2 fastest nodes as a pair, the thruput is around 9000 inserts/second.

What is a good to excellent hardware config for Cassandra?  I have separate drives for data
and commit log and 8GB in 3 machines (all dual core).  My fastest insert node has 4GB and
a triple core processor.

I've run py_stress, and my C++ code beats it by several 1000 inserts/second toward the end
of the runs, so I don't think it is my app, and I've removed the super columns per some suggestions

When Cassandra is working, it performs well, the problem is that is frequently slows down
to < 50% of its peaks and occasionally slows down to 0 inserts/second which greatly reduces
aggregate thruput.

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