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From Michael Stack <st...@duboce.net>
Subject Re: HBase read performance
Date Wed, 12 Nov 2008 05:37:34 GMT
 wrote:
>  
>
>
>
>
> 2008-11-12"Michael Stack" <stack@duboce.net> д
>   
>>  wrote:
>>     
>>> hello, every one. i used to test the performance in PE, but the performance is
not well enough. 
>>>       
>> Please say more.  What kind of numbers were you getting?
>>
>>     
>>> especially, the table format is not as what i need. so, i create a table and
write some string in every cell. then, i use the count , the count time is the count_1 time.

>>> after all, i count all the tables again, the count time is the count_2 time.
count_2 time is almost half of the count_1 time!
>>>
>>> i do not know why this happened, perhaps cache?
>>>   
>>>       
>> Perhaps. If you enable DEBUG and look in the regionserver log, you can 
>> see log of cache hits and misses.  Try and get general sense of how 
>> first run compares to second.  Are your reads random or serial?  If 
>> serial, then yeah, cache is going to help.
>>     
> thanks, i am a new comer
> when the data would be in cache? some times , the count time is never change!
>   

Are you using hbase TRUNK? If so, and if your checkout was recent, 
you'll see benefit/disadvantage of cache.


>>> 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?



17seconds, 13.5seconds and 7.2seconds are not what we usually see. Tell 
us more about your hardware setup.

Thanks,
St.Ack

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