On Mon, May 14, 2012 at 10:52 AM, walt <w41ter@gmail.com> wrote:
> On 05/13/2012 02:00 PM, Michael Mol wrote:
>> On Sun, May 13, 2012 at 4:28 PM, walt <w41ter@gmail.com> wrote:
>>> > I have a usb3 docking station which is showing some behavior I don't
>>> > understand:
>>> >
>>> > *#hdparm -t /dev/sdc
>>> >
>>> > /dev/sdc:
>>> > *Timing buffered disk reads: 266 MB in *3.01 seconds = *88.43 MB/sec
>>> > *Timing buffered disk reads: 266 MB in *3.02 seconds = *88.10 MB/sec
>>> > *Timing buffered disk reads: 306 MB in *3.01 seconds = 101.72 MB/sec
>>> > *Timing buffered disk reads: 266 MB in *3.00 seconds = *88.59 MB/sec
>>> > *Timing buffered disk reads: 306 MB in *3.00 seconds = 101.84 MB/sec
>>> > *Timing buffered disk reads: 306 MB in *3.00 seconds = 101.86 MB/sec
>>> >
>>> > That's all the same disk, repeating hdparm as fast as I could. *The
>>> > disk was not even mounted at the time, and no other disks were active.
>>> >
>>> > Two very different but reproducible numbers, changing values at random
>>> > times. *The only thing I can think of is that the disk may be doing
>>> > a SMART self-test, but for some reason the USB connection prevents
>>> > me from accessing the data so I can't test my theory.
>>> >
>>> > Any other ideas?
>
>> bonnie++?
>
> As Volker suggested, I'm not worried about this but I'm always up for
> learning new stuff, so I tried bonnie++ on the machine's main hard
> drive and on the outboard docking station (both Western Digital).
>
> Here is bonnie's printout for each drive. *Can you tell which is which?
> (They must have hired a special consultant to design the format
Yeah, Bonnie++'s output format is a PITA in some environments. It's
just a table, but it's almost unreadable with variable-width type, and
it's worse when it wraps. I had to copy it into a text editor to be
able to read it.
>
> Version *1.96 * * * ------Sequential Output------ --Sequential Input- --Random-
> Concurrency * 1 * * -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
> Machine * * * *Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP */sec %CP
> a6 * * * * * * * 7G * 403 *97 77669 *10 36911 * 7 *2820 *83 104831 *11 225.0 * 4
> Latency * * * * * * 38221us * *1376ms * * 681ms * 68894us * * 160ms * * 965ms
> Version *1.96 * * * ------Sequential Create------ --------Random Create--------
> a6 * * * * * * * * *-Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
> * * * * * * *files */sec %CP */sec %CP */sec %CP */sec %CP */sec %CP */sec %CP
> * * * * * * * * 16 17246 *25 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++
> Latency * * * * * * *2363us * * 563us * * 653us * * 157us * * *10us * * 238us
> 1.96,1.96,a6,1,1337025021,7G,,403,97,77669,10,3691 1,7,2820,83,104831,11,225.0,4,16,,,,,17246,25,++++ +,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,3822 1us,1376ms,681ms,68894us,160ms,965ms,2363us,563us, 653us,157us,10us,238us
>
>
>
> Version *1.96 * * * ------Sequential Output------ --Sequential Input- --Random-
> Concurrency * 1 * * -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
> Machine * * * *Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP */sec %CP
> a6 * * * * * * * 7G * 714 *99 92174 *11 24808 * 4 *3938 *96 112295 *14 128.1 * 3
> Latency * * * * * * 11493us * *1582ms * * 233ms * 25883us * 22036us * *5344ms
> Version *1.96 * * * ------Sequential Create------ --------Random Create--------
> a6 * * * * * * * * *-Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
> * * * * * * *files */sec %CP */sec %CP */sec %CP */sec %CP */sec %CP */sec %CP
> * * * * * * * * 16 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++
> Latency * * * * * * *2515us * * 517us * *2818us * *1271us * * *18us * * 293us
> 1.96,1.96,a6,1,1337028303,7G,,714,99,92174,11,2480 8,4,3938,96,112295,14,128.1,3,16,,,,,+++++,+++,+++ ++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,114 93us,1582ms,233ms,25883us,22036us,5344ms,2515us,51 7us,2818us,1271us,18us,293us
I'd guess the second printout is the USB drive. It has a much higher
latency on the sequential input test. But that's the only big
difference I can spot.
And I'd disagree with Volker on the "It's USB..." assessment. USB3 is
a _very_ different animal from earlier versions. You get nice things
like DMA, and your CPU usage is far lower than USB2, since the CPU
doesn't have to poll the USB controller for status updates. Honestly,
I'm very impressed at how similar those two printouts look, stat wise.
It's a close call to be able to identify which is which, and I'm not
really confident I did.
--
:wq
Curious hdparm results
