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The vxbench behavior with linux iostat

It is so strange that the vxbench_rhel6_x86_64 program can run successfully and output the result at last, but the system iostat always shows zero during the running process !
Notes: I have tested this with many RHEL5/6 systems, but the same result! It seems that the vxbench for linux does not "support"  the system iostat!


[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]# nohup ./vxbench_rhel6_x86_64 -w read -i maxfilesize=5000m,nthreads=1,iosize=512,nrep=600000 /dev/sdh > vxbench_sd.out 2>&1 &
[1] 19805
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]# iostat -d sdh 1 6
Linux 2.6.18-194.el5 (RHNBWZ3) 01/06/2019

Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sdh 8.50 8.00 0.50 854103674 53366885

Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sdh 0.00 0.00 0.00 0 0

Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sdh 0.00 0.00 0.00 0 0

Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sdh 0.00 0.00 0.00 0 0

Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sdh 0.00 0.00 0.00 0 0

Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sdh 0.00 0.00 0.00 0 0

[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]# iostat -d sdh 1 6
Linux 2.6.18-194.el5 (RHNBWZ3) 01/06/2019

Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sdh 8.50 8.00 0.50 854103674 53366885

Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sdh 0.00 0.00 0.00 0 0

Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sdh 0.00 0.00 0.00 0 0

Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sdh 0.00 0.00 0.00 0 0

Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sdh 0.00 0.00 0.00 0 0

Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sdh 0.00 0.00 0.00 0 0

[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#
[1]+ Done nohup ./vxbench_rhel6_x86_64 -w read -i maxfilesize=5000m,nthreads=1,iosize=512,nrep=600000 /dev/sdh > vxbench_sd.out 2>&1
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]# tail vxbench_sd.out
total1: 50.348 sec 6101539.15 KB/s cpu: 50.01 sys 0.31 user
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#

2 Replies
Highlighted

Re: The vxbench behavior with linux iostat

You might be hitting the cache, all the time. hence no real reads from
the disk,

Try doing some writes with sync and then read.

Highlighted

Re: The vxbench behavior with linux iostat

Even using with -o sync write,  the output of the corresponding iostat still does not take effect!
It seems that vxbench_x86 only supports -o sync for write to bypass the OS cache, but not for read!

So now I wonder whether the vxbench_x86 for linux supports the iostat for the native LVM?


[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]# ./vxbench_rhel6_x86_64 -w write -i maxfilesize=5000m,nthreads=1,iosize=512,nrep=600 /install/nbu/ESD_NB_7.0_CLIENTS_FA.tar.orig
total1: 0.115 sec 2672419.79 KB/s cpu: 0.11 sys 0.00 user
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]# ./vxbench_rhel6_x86_64 -w write -o sync -i maxfilesize=5000m,nthreads=1,iosize=512,nrep=600 /install/nbu/ESD_NB_7.0_CLIENTS_FA.tar.orig
total1: 49.584 sec 6195.58 KB/s cpu: 0.38 sys 0.00 user
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#

 


avg-cpu: %user %nice %system %iowait %steal %idle
40.32 0.00 0.09 0.17 0.00 59.42

Device: tps MB_read/s MB_wrtn/s MB_read MB_wrtn
vgroot-lvinstall
0.22 0.00 0.00 81749 14138

avg-cpu: %user %nice %system %iowait %steal %idle
0.12 0.00 6.49 1.00 0.00 92.39

Device: tps MB_read/s MB_wrtn/s MB_read MB_wrtn
vgroot-lvinstall
0.00 0.00 0.00 0 0

avg-cpu: %user %nice %system %iowait %steal %idle
0.06 0.00 6.25 1.00 0.00 92.69

Device: tps MB_read/s MB_wrtn/s MB_read MB_wrtn
vgroot-lvinstall
131.00 0.00 0.51 0 0

avg-cpu: %user %nice %system %iowait %steal %idle
1.31 0.00 6.31 2.44 0.00 89.94

Device: tps MB_read/s MB_wrtn/s MB_read MB_wrtn
vgroot-lvinstall
128.00 0.00 0.50 0 0

avg-cpu: %user %nice %system %iowait %steal %idle
0.06 0.00 6.30 0.00 0.00 93.63

Device: tps MB_read/s MB_wrtn/s MB_read MB_wrtn
vgroot-lvinstall
0.00 0.00 0.00 0 0

avg-cpu: %user %nice %system %iowait %steal %idle
0.06 0.00 6.24 1.19 0.00 92.51

Device: tps MB_read/s MB_wrtn/s MB_read MB_wrtn
vgroot-lvinstall
0.00 0.00 0.00 0 0

 

[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]# ./vxbench_rhel6_x86_64 -w read -o sync -i maxfilesize=5000m,nthreads=1,iosize=512,nrep=600 /install/nbu/ESD_NB_7.0_CLIENTS_FA.tar.orig
total1: 0.076 sec 4015738.77 KB/s cpu: 0.07 sys 0.00 user
[root@RHNBWZ3 tmp]#
[root@RHNBWZ3 tmp]#