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From Michael Stack <st...@duboce.net>
Subject Re: HBase read performance
Date Wed, 12 Nov 2008 15:09:17 GMT
 wrote:
>   
>> Are you using hbase TRUNK? If so, and if your checkout was recent, 
>> you'll see benefit/disadvantage of cache.
>>     
> hadoop 0.18.1, hbase 0.18.0. I do not use TRUNK , any useful update?
> what do you mean the disadvantage of cache?
>   
Disadvantage is that if you are getting mostly cache-misses, then you 
will be paying the price of filling the cache but getting no benefit.

There is no data block cache in 0.18.x (by default) so this is not the 
issue here. Ignore my comments on cache effect from earlier.

>>     
>>>>> column 	row 	  cell 	write  	count_1  	count_2 
>>>>> 10	     10000	   10B 	 17.2        13.5	         7.2
>>>>> 10	     10000	   50B 	 17	        13.1	         7.3
>>>>> 10	     10000	   200B     19.7	        13.6	         7.6
>>>>> 10	   100000	  10B 	128.4	131.5	74.7
>>>>> 10	   100000	  50B 	134.6	143.1	66.2
>>>>> 10	   100000	  200B      138.1	100.1	77.3
>>>>>
>>>>>   
>>>>>       
>>>>>           
>>>> What is above saying?  That in column 10, you wrote 1000 items of size 
>>>> ten bytes?  The write took 17.2ms, first read 13.5ms and the second 7.2ms?
>>>>
>>>>     
>>>>         
>>> sorry, i did not explain this clearly. there is 10 columns in the table, 10000
rows in a column ,and the 10Bytes in a row
>>> the time is 17s, 13.5s, 7.2s
>>>
>>>   
>>>       
>> 10000 rows in a column? Do you mean 10000 rows in the table and each row 
>> has an entry in the column? Or do you mean 10 rows in the table and each 
>> row has 10000 columns?
>>
>>     
> 10000 rows in the table and each row has an entry in the column
>   

Then the numbers would seem to be way off. Something else must be going 
on. Is the machine swapping?


> DELL PowerEdge 430 , P4 2.8G, 1G Memory. Tooooo poor
>   
Is the machine swapping? Are the datanodes running on same machines?

St.Ack

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