On Fri, May 24, 2002 at 10:23:22AM +0200, Seth Mos wrote:
> [...]
> Software raid5 will give you a much better performance. And if you make it
> with an external log onto the raid1(hardware) device it will perform a few
> hundred percent better then the hardware raid5 of the controller.
I don't have a comparison of hardware vs. software raid, but I did
experiment with various software raid5+XFS configurations. All tests
were on a single 400 MHz CPU with 6 13GB IDE (old, slowwww 7 MB/sec
drives). This is our oldest RAID... no one would let me do "experiments"
on our newer >1TB configurations :-( We have been running the 2.4.16
kernel with XFS.
o 2.4.18+XFS-1.1 shows significant performance improvements,
especially in copying small files (30% faster) and removing
lots of files (300% faster.) This is with an internal log.
o Switching to an external log (as raid1 on partitions of two of the
same six disks that have the raid5) boosted small-file performance
by another 80% or so, even compared to an internal log with the
same 2.4.18 kernel. So, even with XFS-1.1, an external log really
helped a lot here.
o In all tests, sustained writes of very large files (which is
mostly what we do) stayed around 19 MBytes/second.
Some charts are below . . .
Be seeing you,
- Sidik
LEGEND for left column:
kversion[raid5chunksize,raid5algorithm,internal/external log]
UNTAR TREE, INCLUDING `sync' AFTER
(Megabytes per second)
0 0.5 1.0 1.5 2.0
2.4.18[32,0,e] *******************************>2.0
2.4.18[32,2,e] *******************************>2.0
2.4.16[32,2,e] ******************************>1.9
2.4.18[64,0,e] ******************************>1.9
2.4.18[128,0e] *******************************>2.0
2.4.16[128,0e] ******************************>1.9
2.4.18[32,0,i] ********************>1.2
2.4.18[32,2,i] ********************>1.2
2.4.16[32,2,i] ********************>1.2
2.4.16[128,0i] **********************>1.4
COPY CACHED TREE, INCLUDING `sync' AFTER
(Megabytes per second)
0 0.5 1.0 1.5 2.0 2.5
2.4.18[32,0,e] **************************************>2.4
2.4.18[32,2,e] ***************************************>2.5
2.4.16[32,2,e] *************************************>2.3
2.4.18[64,0,e] ******************************************>2.8
2.4.18[128,0e] *****************************************>2.7
2.4.16[128,0e] ****************************************>2.6
2.4.18[32,0,i] **********************>1.4
2.4.18[32,2,i] *************************>1.6
2.4.16[32,2,i] ****************>1.1
2.4.16[128,0i] ***************>1.0
REMOVE TREE
(Files removed per second)
0 250 500 750 1000
2.4.18[32,0,e] *********************************>1050
2.4.18[32,2,e] **********************************>1150
2.4.16[32,2,e] ********************>600
2.4.18[64,0,e] **********************************>1150
2.4.18[128,0e] **********************************>1150
2.4.16[128,0e] ******************>550
2.4.18[32,0,i] ***************>400
2.4.18[32,2,i] ***********>300
2.4.16[32,2,i] ****>100
2.4.16[128,0i] ***>90
SUSTAINED LARGE FILE WRITE
(Megabytes per second)
0 5 10 15 20
2.4.18[32,0,e] *********************************>20
2.4.18[32,2,e] ********************************>19
2.4.16[32,2,e] ********************************>19
2.4.18[64,0,e] *******************************>18
2.4.18[128,0e] ******************************>17
2.4.16[128,0e] ******************************>17
2.4.18[32,0,i] *******************************>18
2.4.18[32,2,i] ********************************>19
2.4.16[32,2,i] *******************************>18
2.4.16[128,0i] ******************************>17
(I apologize for not using bonnie or something standard ... I
untarred linux-2.4.18.tgz, sync'd, divided the time into 150MB,
cp -a linux linux2 + sync, divided into 150MB, and time rm -r
linux divided into the number of files in the source tree.)
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