FreeBSD MySQL still WAY slower than Linux
Paul Mather
paul at gromit.dlib.vt.edu
Tue Jun 28 15:38:54 GMT 2005
On Tue, 2005-06-28 at 11:21 +0200, Roman Neuhauser wrote:
> # olli at lurza.secnetix.de / 2005-06-21 16:51:10 +0200:
> > For accurate measurements and comparisons, you have to make
> > sure to use _exactly_ the same physical location on the
> > disk.
>
> No you don't. You want to make a side-by-side comparison
> of two products, and if one of them underperforms, it just
> underperforms. You cannot use a poor location selection
> strategy in the driver as an excuse for poor operation.
The point people are making is that location can have a significant
effect on performance, and so should not be dismissed out of hand.
Here is what I get when I run diskinfo on one of the (somewhat elderly)
disks I use in my desktop system (this is a drive I use for data, and it
is idle):
zappa# diskinfo -tv /dev/ad4
/dev/ad4
512 # sectorsize
25590620160 # mediasize in bytes (24G)
49981680 # mediasize in sectors
49585 # Cylinders according to firmware.
16 # Heads according to firmware.
63 # Sectors according to firmware.
Seek times:
Full stroke: 250 iter in 5.159189 sec = 20.637 msec
Half stroke: 250 iter in 4.206125 sec = 16.825 msec
Quarter stroke: 500 iter in 7.151951 sec = 14.304 msec
Short forward: 400 iter in 2.794380 sec = 6.986 msec
Short backward: 400 iter in 4.135579 sec = 10.339 msec
Seq outer: 2048 iter in 0.332711 sec = 0.162 msec
Seq inner: 2048 iter in 0.363152 sec = 0.177 msec
Transfer rates:
outside: 102400 kbytes in 7.677977 sec = 13337 kbytes/sec
middle: 102400 kbytes in 9.151475 sec = 11189 kbytes/sec
inside: 102400 kbytes in 14.345492 sec = 7138 kbytes/sec
Note how the transfer rate for the "outside" is almost twice that of the
"inside." Suppose I run tests on two different operating systems, one
of which resides in a partition on the "inside" portion and the other in
one on the "outside" portion. (Note that however good or bad it may be,
the "location selection strategy in the driver" can only lay out data
within the confines of the partition.) Now, I do a "dd" test and find
that the "outside" OS is almost twice as fast as the other. Would it be
wise to conclude that the slower OS is woefully inefficient compared to
the faster one? Suppose both tests turn out to take roughly the same
time. Should I conclude that the OS residing on the "inside" is just as
efficient as the other OS?
Cheers,
Paul.
--
e-mail: paul at gromit.dlib.vt.edu
"Without music to decorate it, time is just a bunch of boring production
deadlines or dates by which bills must be paid."
--- Frank Vincent Zappa
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