I am investigating slow application issues with some New Hardware and am running into some odd results. I am trying to determine what is causing this behavior.
I am using
dd if=x.b1 of=x.b10 bs=8192 oflag=dsync
of a 101MB file simulate how our database is writing to disk (the
dsync flag was suggested by our database vendor), and while normal dd commands without the dsync option are showing 80-100 Mb/s, with the dsync command I am getting results in the 160Kb/s-200Kb/s range.
This behavior has been viewed on multiple pieces of hardware, as well as different model hard drives and doing a drive wipe test
dd if=/dev/zero of=/dev/sda bs=8192 oflag=dsync
shows more expected 80-100Mb/s speed, which seems to suggest it is something in our custom OS that is slowing things down. We have run these tests under a custom SuseLinux as well as OracleOS (32 and 64 bit) and we continue to see these very low numbers.
Can you give me some ideas of where the problem is?