Neat trick

I figured out how to speed up the sequential scans using "blockdev"
command. Essentially, this increases the read-ahead on the underlying
block device for the file system. It will change the read-ahead value
for the entire disk, even if there are several partitions on the disk.
The results are very promising. Unfortunately, I didn't take baseline
numbers and measure the effect with precision, but the look of it is
that things are much faster with the read-ahead set to 2048 instead of
the default 256. The read-ahead is measured in sectors read ahead by the
OS. The OS is Red Hat Linux, EL 5.5.

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Mladen Gogala
Sr. Oracle DBA
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