PE 6660 : Hardware Raid 0 w/ Software Raid 1

Rechenberg, Andrew ARechenberg at shermanfinancialgroup.com
Tue Jan 27 07:31:00 CST 2004


[snip]

> I decided to take a look at the logical drive settings on the 
> Perc card and changed each of the disks from write-back to 
> write-through and re-ran the tests with an increase in speed 
> of almost 300%. So, for raid 0 setups, it looks like 
> write-through is the way to go.
> 
> bonnie++ v1.03 was used for the testing with the options:
> "-s 22616 -d . -n 0"
> 
> Here are the results with write-back enabled:
> 
> Version  1.03	------Sequential Output------ --Sequential 
> Input- --Random-
> 		-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
> server   22616M 31198 100 31871  10 26423  11 27005  82 79125 
>  18 534.1  1
> 
> server,22616M,31198,100,31871,10,26423,11,27005,82,79125,18,53
> 4.1,1,,,,,,,,,,,,,
> 
> Here are the results with write-through enabled:
> 
> Version  1.03	------Sequential Output------ --Sequential 
> Input- --Random-
>                 -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
> server   22616M 30735 100 91289  30 50829  18 31485  96 
> 205497 39 630.1  1
> 
> server,22616M,30735,100,91289,30,50829,18,31485,96,205497,39,6
> 30.1,1,,,,,,,,,,,,,
> 

We have found that the following settings give the best performance with
PERC3/[QD]Cs:

WRITE-THRU
NOREADAHEAD

And on Windows servers setting the controller to I2O mode from
MASS-STORAGE.  

We actually ditched the hardware RAID controllers altogether and now use
software RAID exclusively.  We experienced over 40% improvement in
sequential read and writes by moving to software RAID10.

Let me know if you have any questions.

Regards,
Andy.


> 
> On Mon, 26 Jan 2004, Steve Mickeler wrote:
> 
> >
> > I've got a PE 6600 setup with AS 2.1 , fully updated, running kernel
> > 2.4.9-e.35
> >
> > Ive got the disks setup as follows:
> >
> > 2 x 73GB disks mirrored for OS on Controller 1, Channel 0
> >
> > 3 x 73GB disks striped for Data on Controller 1, Channel 0
> >
> > 3 x 73GB disks striped for Data on Controller 2, Channel 0
> >
> > I then use software raid in linux to mirror the 2 hardware raid 0 
> > logical devices for redundancy as you can't mirror across 
> controllers 
> > with the perc 3di cards.
> >
> > Is there anything with the setup that raises any eyebrows ?
> >
> > If not, any reason I'm only seeing 35MB/sec while writing 
> to the mirror ?
> >
> > I'm just about to break the mirror and run my tests on the 
> individual 
> > raid 0 device to see if the bottleneck is at the software 
> or hardware 
> > level.
> >
> >
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