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Mladen Gogala wrote:
> On Wed, 08 Feb 2006 23:35:14 -0800, Wyvern wrote:
>
>> I´ve not understood very well the IO Scheduler function but I´ll read >> more about it ...
Hi Mladen,
actually the I/O scheduler(s) works even if the I/O request are not
simultaneous.
typical is the merging of I/O for sequential reads or writes.
The advantages can be tremendous.
Here is an example (same hardware, same device):
time dd if=/dev/zero of=/dev/raw/raw3 bs=8k count=10000
10000+0 records in
10000+0 records out
real 0m41.063s
user 0m0.016s
sys 0m0.412s
time dd if=/dev/zero of=/u02/foo bs=8k count=10000
10000+0 records in
10000+0 records out
real 0m2.324s user 0m0.005s sys 0m0.536s
The second dd has its I/O merged.
Consider this controversial but the I/O scheduler eliminate the need to have oracle block size "aligned" to file system block size (even without direct I/O).
Regards
-- Fabrizio Magni fabrizio.magni_at_mycontinent.com replace mycontinent with europeReceived on Thu Feb 09 2006 - 08:14:20 CST