Re: Re: wo did some test on cassandra ,but the result puzzled us

[Bingbing Liu]

the difference between se and random the test code is just how the key of each 
record is generated.

the test code is :

 
long totalSWriteTime = 0;
for (int i = 0; i < totalRows; i++) {
byte[] key = dg.getRandomRow();//when sequential write , we use i as the key
byte[] data = dg.generateValue();
long start = System.currentTimeMillis();
client.insert("Keyspace1", new String(key), new ColumnPath(
"Standard1", null, "data".getBytes("UTF-8")), data,timestamp, 
ConsistencyLevel.ONE);
totalSWriteTime += (System.currentTimeMillis() - start);
    if(i % 10000 == 0){
System.out.println("Has write " + i);
    }
}

is there something wrong?
2010-03-12 



Bingbing Liu 



发件人： Jonathan Ellis 
发送时间： 2010-03-12  13:40:40 
收件人： cassandra-dev 
抄送： 
主题： Re: wo did some test on cassandra ,but the result puzzled us 
 
why reads are slower than writes:
http://wiki.apache.org/cassandra/FAQ#reads_slower_writes
no idea on seq vs random.  i would not be surprised if there is a bug
in your test code.
On Fri, Mar 12, 2010 at 12:36 AM, Bingbing Liu <rucb...@gmail.com> wrote:
> We did some test on on Cassandra, and the benchmark is from Section 7 of the 
> BigTable paper “Bigtable: A Distributed Storage System for Structured Data”, 
> the benchmark task includes: random write, random read, sequential write, and 
> sequential read. The test results made us puzzled. We use a cluster of 5 
> nodes (each node has a 4 cores cpu , 4G memory).The data for test is a table 
> with 4,000,000  records each of which is 1000 bytes. The test results are as 
> follows:
> Sequential write:  875124 ms
> Sequential read:  1972588 ms
> Random read:  43331738 ms
> Random write:  20193484 ms
> We wondered why the speed of sequential write are so faster than the speed of 
> sequential read, and why the speed of sequential write are so faster than 
> that of random write? We think that the speed of read should be faster than 
> that of data write, but the results are just the opposite, would you please 
> give us some explanations, thanks a lot!
>
> 2010-03-12
>
>
>
> Bingbing Liu
>