Actually there are 2 read aheads in linux (from what I learned last time, I
did benchmarking on random reads). One is the filesystem readahead which
linux does and then there is also a disk level read ahead which can be
modified by using the hdparm command. IIRC, there is no sure way of
removing filesystem level readaheads but disk level read aheads can be

For regular HDDs, if you are reading small keys, don't think changing the
disk level read ahead will make a big difference because the seek latency
will dominate. However, for SSDs, it did help to reduce the disk level read
ahead in my tests - because the seek latency is small and reading a lot of
unnecessary data is relatively expensive.
On Sat, Feb 1, 2014 at 11:07 PM, Vladimir Rodionov
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