RE: I/O and db_file_multiblock_read_count

/dev/null is hard, as some OS'es, solaris notably, do evil tricks with
certain utilities (like cat something to /dev/null - it returns
immediately).  Not sure about dd


________________________________

        From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Kevin Closson
        Sent: Tuesday, December 12, 2006 12:35 PM
        To: oracle-l
        Subject: RE: I/O and db_file_multiblock_read_count
        
        
        I would have never though a write to /dev/zero would work...I
learn something new every day.
        Can you try this test writing to /dev/null?


________________________________

                From: Jesse, Rich [mailto:Rich.Jesse@xxxxxx] 
                Sent: Tuesday, December 12, 2006 7:16 AM
                To: kevinc@xxxxxxxxxxxxx; oracle-l
                Subject: RE: I/O and db_file_multiblock_read_count
                
                
                I'm guessing that I'm limited by CPU on this IBM JS21
blade's LPAR (MPV, 2 cores max) with an SVC (virtualized SAN) backend.
topas showed kernel mode CPU >95% for most of the tests.
                 
                /oracle $ time dd if=S.dbf of=/dev/zero bs=1024k
                16384+1 records in
                16384+1 records out
                 
                real    1m3.044s
                user    0m0.271s
                sys     0m42.458s
                
                /oracle $ time dd if=S.dbf of=/dev/zero bs=1024k
                16384+1 records in

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