List:Internals« Previous MessageNext Message »
From:Michael Widenius Date:March 5 2001 8:08pm
Subject:Re: scsi vs ide performance on fsync's
View as plain text  
Hi!

>>>>> "Mike" == Mike Black <mblack@stripped> writes:

Mike> Here's a strace -r on IDE:
Mike>      0.001488 write(3, "\214\1\0\0Blah Blah Blah Blah Blah Bla"..., 56) = 56
Mike>      0.000516 fdatasync(0x3)            = 0
Mike>      0.001530 write(3, "\215\1\0\0Blah Blah Blah Blah Blah Bla"..., 56) = 56
Mike>      0.000513 fdatasync(0x3)            = 0
Mike>      0.001555 write(3, "\216\1\0\0Blah Blah Blah Blah Blah Bla"..., 56) = 56
Mike>      0.000517 fdatasync(0x3)            = 0
Mike>      0.001494 write(3, "\217\1\0\0Blah Blah Blah Blah Blah Bla"..., 56) = 56
Mike>      0.000515 fdatasync(0x3)            = 0
Mike>      0.001495 write(3, "\220\1\0\0Blah Blah Blah Blah Blah Bla"..., 56) = 56
Mike>      0.000522 fdatasync(0x3)            = 0

Mike> Here it is on SCSI:
Mike>      0.049285 write(3, "\3\0\0\0Blah Blah Blah Blah Blah Bla"..., 56) = 56
Mike>      0.000689 fdatasync(0x3)            = 0
Mike>      0.049148 write(3, "\4\0\0\0Blah Blah Blah Blah Blah Bla"..., 56) = 56
Mike>      0.000516 fdatasync(0x3)            = 0
Mike>      0.049318 write(3, "\5\0\0\0Blah Blah Blah Blah Blah Bla"..., 56) = 56
Mike>      0.000516 fdatasync(0x3)            = 0
Mike>      0.049343 write(3, "\6\0\0\0Blah Blah Blah Blah Blah Bla"..., 56) = 56

Mike> Looks like a constant 50ms delay on each fdatasync() on SCSI vs .5ms for
Mike> IDE.  Maybe IDE isn't really doing a sync??  I find .5ms to be a little too
Mike> good.

I wonder from where the fdatasync() is comming;  MySQL is not doing
those (if you are not running mysqld with --flush)

Mike> I did this on 4 different machines with different SCSI cards (include RAID5
Mike> and non-RAID), disks, and IDE drives with the same behavior.

Regards,
Monty
Thread