IBM TotalStorage DS6000 Series: Performance Monitoring and Tuning

Chapter 7. Open systems servers - UNIX 229

The following command will perform sequential writes to your LUNs:

dd if=/dev/zero of=/dev/rvpath0 bs=128k

dd if=/dev/zero of=/dev/rvpath0 bs=1024k

time dd if=/dev/zero of=/dev/rvpath0 bs=128k count=781

Try different block sizes, different raw vpath devices, combinations of reads and writes. Run

the commands against the block device (/dev/vpath0) and notice that block size does not

affect performance.

7.7.2 Verifying your system

So far, we have just been playing around with the dd command. But the next section, 7.8,

“Volume groups, logical volumes and file systems” on page 233, will explore the use of the

LVM of the UNIX operating system to configure DS6000 storage for best performance. At

each step along the way, there are tests that should be run to test the storage infrastructure.

We will discuss these tests here so that you will be equipped with some testing techniques as

you configure your storage for best performance.

Verify the storage subsystem

After the LUNs have been assigned to the host system, and multipathing software like SDD

has discovered the LUNs, it is important to test the storage subsystem. The storage

subsystem includes the SAN infrastructure, the host system HBAs, the DS6000.

1. The first step is to run the following command to review that your storage allocation from

the DS6000 is working well with SDD:

datapath query essmap

Make sure what LUNs you have is what you expect. Are there the correct number of paths

to the LUNs? Are all the LUNs from different Ranks? Are the LUN sizes correct? Output

from the command looks like that in Example 7-25.

Example 7-25 datapath query essmap command output

{CCF-part2:root}/tmp/perf/scripts -> datapath query essmap

Disk Path P Location adapter LUN SN Type Size LSS Vol Rank C/A S Connection port RaidMode

------- ----- - ----------- ------ ----------- ------------ ---- ---- --- ----- ---- - ----------- ---- --------

vpath0 hdisk4 7V-08-01[FC] fscsi0 75065513000 IBM 2107-900 10.7 48 0 0000 0e Y R1-B2-H1-ZA 100 RAID10

vpath0 hdisk12 7V-08-01[FC] fscsi0 75065513000 IBM 2107-900 10.7 48 0 0000 0e Y R1-B2-H1-ZB 101 RAID10

vpath0 hdisk20 7k-08-01[FC] fscsi1 75065513000 IBM 2107-900 10.7 48 0 0000 0e Y R1-B1-H3-ZC 32 RAID10

vpath0 hdisk28 7k-08-01[FC] fscsi1 75065513000 IBM 2107-900 10.7 48 0 0000 0e Y R1-B1-H3-ZD 33 RAID10

vpath1 hdisk5 7V-08-01[FC] fscsi0 75065513001 IBM 2107-900 10.7 48 1 fffe 0e Y R1-B2-H1-ZA 100 RAID10

vpath1 hdisk13 7V-08-01[FC] fscsi0 75065513001 IBM 2107-900 10.7 48 1 fffe 0e Y R1-B2-H1-ZB 101 RAID10

vpath1 hdisk21 7k-08-01[FC] fscsi1 75065513001 IBM 2107-900 10.7 48 1 fffe 0e Y R1-B1-H3-ZC 32 RAID10

vpath1 hdisk29 7k-08-01[FC] fscsi1 75065513001 IBM 2107-900 10.7 48 1 fffe 0e Y R1-B1-H3-ZD 33 RAID10

vpath2 hdisk6 7V-08-01[FC] fscsi0 75065513002 IBM 2107-900 10.7 48 2 fffc 0e Y R1-B2-H1-ZA 100 RAID10

vpath2 hdisk14 7V-08-01[FC] fscsi0 75065513002 IBM 2107-900 10.7 48 2 fffc 0e Y R1-B2-H1-ZB 101 RAID10

vpath2 hdisk22 7k-08-01[FC] fscsi1 75065513002 IBM 2107-900 10.7 48 2 fffc 0e Y R1-B1-H3-ZC 32 RAID10

vpath2 hdisk30 7k-08-01[FC] fscsi1 75065513002 IBM 2107-900 10.7 48 2 fffc 0e Y R1-B1-H3-ZD 33 RAID10

vpath3 hdisk7 7V-08-01[FC] fscsi0 75065513003 IBM 2107-900 10.7 48 3 fffa 0e Y R1-B2-H1-ZA 100 RAID10

vpath3 hdisk15 7V-08-01[FC] fscsi0 75065513003 IBM 2107-900 10.7 48 3 fffa 0e Y R1-B2-H1-ZB 101 RAID10

vpath3 hdisk23 7k-08-01[FC] fscsi1 75065513003 IBM 2107-900 10.7 48 3 fffa 0e Y R1-B1-H3-ZC 32 RAID10

vpath3 hdisk31 7k-08-01[FC] fscsi1 75065513003 IBM 2107-900 10.7 48 3 fffa 0e Y R1-B1-H3-ZD 33 RAID10

vpath4 hdisk8 7V-08-01[FC] fscsi0 75065513100 IBM 2107-900 10.7 49 0 ffff 17 Y R1-B2-H1-ZA 100 RAID10

vpath4 hdisk16 7V-08-01[FC] fscsi0 75065513100 IBM 2107-900 10.7 49 0 ffff 17 Y R1-B2-H1-ZB 101 RAID10

vpath4 hdisk24 7k-08-01[FC] fscsi1 75065513100 IBM 2107-900 10.7 49 0 ffff 17 Y R1-B1-H3-ZC 32 RAID10

vpath4 hdisk32 7k-08-01[FC] fscsi1 75065513100 IBM 2107-900 10.7 49 0 ffff 17 Y R1-B1-H3-ZD 33 RAID10

vpath5 hdisk9 7V-08-01[FC] fscsi0 75065513101 IBM 2107-900 10.7 49 1 fffd 17 Y R1-B2-H1-ZA 100 RAID10

vpath5 hdisk17 7V-08-01[FC] fscsi0 75065513101 IBM 2107-900 10.7 49 1 fffd 17 Y R1-B2-H1-ZB 101 RAID10

vpath5 hdisk25 7k-08-01[FC] fscsi1 75065513101 IBM 2107-900 10.7 49 1 fffd 17 Y R1-B1-H3-ZC 32 RAID10

vpath5 hdisk33 7k-08-01[FC] fscsi1 75065513101 IBM 2107-900 10.7 49 1 fffd 17 Y R1-B1-H3-ZD 33 RAID10

Caution: Use extreme caution when using the dd command to perform a sequential write

operation. Ensure the dd is not writing to a device file that is part of the UNIX operating

system.