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From Mark Jones <MJo...@imagehawk.com>
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
yesterday.

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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