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From "B. Todd Burruss" <bburr...@real.com>
Subject Re: memory question
Date Wed, 24 Mar 2010 19:10:43 GMT
no compaction.

Jonathan Ellis wrote:
> did you check jmx to see if a compaction is going on?
>
> On Mon, Mar 22, 2010 at 5:14 PM, Todd Burruss <bburruss@real.com> wrote:
>   
>> after running my cluster for a while performance has become unacceptable,
>> 200+ ms for reads.  if running well, i see reads <10ms.  when i run iostat
>> the disk is being hammered by reads.  seems like i/o caching isn't even
>> being used
>>
>> avg-cpu:  %user   %nice %system %iowait  %steal   %idle
>>            2.81    0.00    1.41   13.62    0.00   82.16
>> Device:         rrqm/s   wrqm/s   r/s   w/s    rMB/s    wMB/s avgrq-sz
>> avgqu-sz   await  svctm  %util
>> cciss/c0d0p1
>>                0.00     0.00  0.00  0.00     0.00     0.00     0.00
>> 0.00    0.00   0.00   0.00
>> cciss/c0d1p1
>>                0.00     0.00 848.50  0.00    13.66     0.00    32.98
>> 21.50   25.23   1.18 100.05
>>
>> i run top and i see cassandra's memory usage as follows:
>>
>>   PID USER     PR NI VIRT  RES SHR S %CPU %MEM    TIME+ COMMAND
>> 31510 bburruss 19  0 359g  37g 27g S 48.8 80.1  2137:30 java
>>
>>
>> i set -Xmx10g so it isn't java using the memory.  is it mmap i/o?  what
>> would be causing the huge memory usage?
>> it seems reasonable that the performance is bad because the i/o cache can't
>> be used properly.
>>
>>     


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