07-03-2012
At the application level page size is an important concept, it's the unit of interaction with the disk. Imagine a database system requesting a record A, it'd be completely inefficient to only read this record (couple of bytes), instead we collocate a bunch of records in a page and we bet on spatial/temporal locality ...
It's a tradeof, if you set the page size to too big, you risk over reading stuff you dont need. Too small, and you risk to get multiple requests for otherwise contiguous records. A bit what the os does with 4096b pages.
I am trying to study that, using a buffered read of different sizes and calculate the throughtput ... I know only basics about disks, but i am certain that the metric i am studying is not uniform, thus doing the math is just meaningless.
I should cope with all parameters(cache,vm,readahead..ect) and have something like:
bs=512b 0.01sec 50kb/s
bs=16kb 0.0004sec 164mb/s
bs=2M 0.01sec 200mb/s
Then i will decide that 16kb is the best time vs throughtput trade off and this will be my page size.
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