MEM: almost 100% (16GB)
-----------------
maybe this is the bottleneck.
writing concerns Memtable and SSTable in memory.

在 2010年6月2日 上午9:48,Shuai Yuan <yuanshuai@supertool.net.cn>写道:
在 2010-06-01二的 15:00 -0500,Jonathan Shook写道:
> Also, what are you meaning specifically by 'slow'? Which measurements
> are you looking at. What are your baseline constraints for your test
> system?
>
Actually, the problem is the utilizaton of resources(for a single
machine):
CPU: 700% / 1600% (16 cores)
MEM: almost 100% (16GB)
Swap: almost 0%
Disk IO(write): 20~30MB / 200MB (7.2k raid5, benchmarked previously)
NET: up to 100Mbps / 950Mbps (1Gbps, tuned and benchmarked previously)

So the speed of generating load, about 15M/s as reported before seems
quite slow to me. I assume the system should get at least about 50MB/s
of Disk IO speed.

MEM? I don't think it plays a major role in this writing game. What's
the bottleneck of the system?

P.S
about Consistency Level, I've tried ONE/DCQUORUM and found ONE is about
10-15% faster. However that's neither a promising result.

Thanks!

Kevin
>
> 2010/6/1 史英杰 <shiyingjie1983@gmail.com>:
> > Hi, It would be better if we know which Consistency Level did you choose,
> > and what is the schema of test data?
> >
> > 在 2010年6月1日 下午4:48,Shuai Yuan <yuanshuai@supertool.net.cn>写道:
> >>
> >> Hi all,
> >>
> >> I'm testing writing speed of cassandra with 4 servers. I'm confused by
> >> the behavior of cassandra.
> >>
> >> ---env---
> >> load-data app written in c++, using libcassandra (w/ modified batch
> >> insert)
> >> 20 writing threads in 2 processes running on 2 servers
> >>
> >> ---optimization---
> >> 1.turn log level to INFO
> >> 2.JVM has 8G heap
> >> 3.32 concurrent read & 128 write in storage-conf.xml, other cache
> >> enlarged as well.
> >>
> >> ---result---
> >> 1-monitoring by `date;nodetool -h host ring`
> >> I add all load together and measure the writing speed by
> >> (load_difference / time_difference), and I get about 15MB/s for the
> >> whole cluster.
> >>
> >> 2-monitoring by `iostat -m 10`
> >> I can watch the disk_io from the system level and have about 10MB/s -
> >> 65MB/s for a single machine. Very big variance over time.
> >>
> >> 3-monitoring by `iptraf -g`
> >> In this way I watch the communication between servers and get about
> >> 10MB/s for a single machine.
> >>
> >> ---opinion---
> >> So, have you checked the writing speed of cassandra? I feel it's quite
> >> slow currently.
> >>
> >> Could anyone confirm this is the normal writing speed of cassandra, or
> >> please provide someway of improving it?
> >> --
> >> Kevin Yuan
> >> www.yuan-shuai.info
> >>
> >>
> >
> >
>

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