# Buffer pool vs database pages

**URL:** <https://forums.percona.com/t/buffer-pool-vs-database-pages/1825>\
**Category:** Other MySQL® Questions\
**Created:** [June 8, 2012, 5:42am UTC](https://forums.percona.com/t/buffer-pool-vs-database-pages/1825 "2012-06-08T05:42:20Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![zack](https://avatars.discourse-cdn.com/v4/letter/z/f6c823/32.png) [@zack](https://forums.percona.com/u/zack)\
**Post date:** [June 8, 2012, 5:42am UTC](https://forums.percona.com/t/buffer-pool-vs-database-pages/1825/1 "2012-06-08T05:42:20Z")

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Hi

How is it possible that the “Database pages” are higher than the actual buffer pool size ?

Mysql Percona Server version 5.5.23-55-log  
Buffer pool size 639999  
Database pages 845454

Isn’t it so that data pages represent the amount of pages in the buffer pool ?  
I also see that the server is using more memory than I have set it up to use in my.cnf

Can this have something to do with using row format compressed ?  
I see this raise in db pages if someone does a really huge dataset fetch from a table with many rows.

## From the innodb status:

## BUFFER POOL AND MEMORY

Total memory allocated 10772480000; in additional pool allocated 0  
Internal hash tables (constant factor + variable factor)  
Adaptive hash index 302005952 (166014536 + 135991416)  
Page hash 10376728 (buffer pool 0 only)  
Dictionary cache 85223713 (41505008 + 43718705)  
File system 1374512 (82672 + 1291840)  
Lock system 25941208 (25940456 + 752)  
Recovery system 0 (0 + 0)  
Dictionary memory allocated 43718705  
Buffer pool size 639999  
Buffer pool size, bytes 10485743616  
Free buffers 0  
Database pages 845454  
Old database pages 312071  
Modified db pages 165  
Pending reads 0  
Pending writes: LRU 0, flush list 0, single page 0  
Pages made young 877727, not young 0  
2.31 youngs/s, 0.00 non-youngs/s  
Pages read 1118257, created 63316, written 1376455  
0.10 reads/s, 0.03 creates/s, 22.78 writes/s  
Buffer pool hit rate 1000 / 1000, young-making rate 3 / 1000 not 0 / 1000  
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s  
LRU len: 845454, unzip\_LRU len: 93501  
I/O sum[4]:cur[0], unzip sum[85]:cur[0]

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<div class="post-metadata">

**Author:** ![gmouse](https://avatars.discourse-cdn.com/v4/letter/g/b9e5f3/32.png) [@gmouse](https://forums.percona.com/u/gmouse)\
**Post date:** [June 14, 2012, 4:25am UTC](https://forums.percona.com/t/buffer-pool-vs-database-pages/1825/2 "2012-06-14T04:25:51Z")

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Buffer pool size is the size in megabytes, the other number indicates the nuber of pages (each is standard 16 kB).

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<div class="post-metadata">

**Author:** ![zack](https://avatars.discourse-cdn.com/v4/letter/z/f6c823/32.png) [@zack](https://forums.percona.com/u/zack)\
**Post date:** [June 14, 2012, 5:22am UTC](https://forums.percona.com/t/buffer-pool-vs-database-pages/1825/3 "2012-06-14T05:22:52Z")

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No that is not correct, this is buffer pool in pages:  
Buffer pool size 639999  
Database pages 845454

And this is bytes:  
Buffer pool size 639999 x 16k = 10485743616  
Buffer pool size, bytes 10485743616