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From Heath Oderman <he...@526valley.com>
Subject Re: RE: Very new user needs some troubleshooting pointers
Date Fri, 09 Apr 2010 16:23:13 GMT
What's interesting for my case is that I put a timer around the thrift
method to insert_batch

Every iteration of that call against debian (any hardware, same network or
in amazon cloud with windows machine in ec2 as well) takes 400,000 ticks.
Super consistent.  One thread.

My friends setup with cassandra on osx takes 400,000 ticks for the first
insert, vthen drops to 20,000 ticks for every consecutive call.

That's what is so strange.

On Apr 9, 2010 12:15 PM, "Mark Jones" <MJones@imagehawk.com> wrote:

 Sounds like we are some experiencing the same problems. (I’m using 0.6RC1)
I have a 3 node cluster with 8GB/machine (dual core CPU).  I’m peaking on
inserts at about 6000-7000/second running 40 threads.  Separate spindles for
commitlog and data…..



My read speed is atrocious, 800/sec sustained (starts off at 1800+/second
and falls back to 800/sec).  Of course that is only if I read from the
“correct” node.  Depending on the moment, 2 of the nodes will return
1-2/second instead of 800, and only one node will return 800/second.  And if
I spread the reads across many nodes, all the performance drops.   nodetool
loadbalance can change which node is the “golden” node, but I don’t know
why.  I have doubled the # of concurrent read threads and seen some
performance improvement, (that was the last thing I tried, and eeked out
another 150/second)



So much about Cassandra makes we WANT it to work, I mean look at the fact
that all nodes are essentially equal, that it replicates from rack to rack,
from DC to DC, now, if I could just make it perform.



My machines are basically idle (a large amount of IOWait, but the time is
spent in the pending queue, vs the device svctime).  So far I’ve got little
insight into what could be wrong, I’ve increased the key cache 10X using
JConsole but the hit rate is still at times abysmal.



I’m writing 400-800 byte blobs with an 8 byte key (supercolumn) and a 12
byte “subkey”, then a 5 byte column name, something that would seem to be
right up Cassandra’s alley.



Right now I’m reworking my test to dump it into MySQL on the same machines,
so I can compare the two for speed, because either I’ve got crap for
hardware, or there is something rotten in Denmark.



*From:* Heath Oderman [mailto:heath@526valley.com]
*Sent:* Friday, April 09, 2010 10:40 AM
*To:* user@cassandra.apache.org
*Subject:* Re: Very new user needs some troubleshooting pointers





Thanks for the reply Jonathan!



I started with multi threaded tests, but when my performance...

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