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STATUS variables: the difference between innodb_pages_read and innodb_buffer_pool_reads

I haven't gotten any responses to my question from Friday, so I figured I'd post a more direct question:

The two variables 'innodb_pages_read' and 'innodb_buffer_pool_reads' are different. 'Innodb_pages_read' seems consistently higher than the buffer_pool_reads. Certainly the buffer pool reads 'pages', but what else would be counted as a page read?

On the flip side, 'innodb_pages_written' and 'innodb_buffer_pool_pages_flushed' seem consistent.

Anyone have any clues?

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It's all about the metrics, but what do they mean?

I'm working on an update to my myq_gadgets package for 5.1, particularly the innodb stats tracker. I'm liking the additional stats that are in SHOW STATUS now for Innodb, particularly because I don't need to parse SHOW INNODB STATUS anymore. I'm in love with being able to compare logical to physical I/Os for the buffer pool.

I'm a bit confused, however, as some of my numbers don't quite line up. Here's what I've got so far:

            | Innodb Engine       Buffer Pool                        Data                     Log       Lock
Time         read  ins  upd  del  new read %phy wrte %phy %dirt wait read      wrte      fsyc wrte fsyc wait time
02/22-10:06  3.8k    0    0    0    0 9.8k  259 15.0  0.1   0.0    0  351 6.6M  0.9 2.6K  0.9  0.7  0.8    0    0
02/22-10:07  5.6k    0    0    0    0  14k  344 21.8  0.1   0.0    0  461 8.7M  1.3 3.9K  1.3  1.0  1.1    0    0

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STATUS variables: the difference between innodb_pages_read and innodb_buffer_pool_reads

It's all about the metrics, but what do they mean?

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