HP XP P9500 Storage - Manual (Page 32)

and for one of the Dev (slices) in that LU, the corresponding logical device
file names of the sd or ssd devices are c2t1d1s0 and c3t2d1s0. In this
case, when you install HDLM, these logical device files will be deleted.
Then, a logical device file that has a different controller number, such as
c4t1d1s0, is created for the HDLM device.
The following explains each part of the logical device file name format
cUtXdYsZ:
U
The controller number reserved by HDLM using a nexus driver
X
The target ID or WWN (World Wide Name) of the sd or ssd device that
corresponds to the HDLM device
Y
The LUN of the sd or ssd device that corresponds to the HDLM device
Z
The device slice number of the sd or ssd device that corresponds to
the HDLM device
Note
In Solaris 9, Solaris 10, or Solaris 11, if EFI labels are set for LUs, the
HDLM logical device name, which represents the entire LU, will be in
the cUtXdY format.
Locations of logical device files for HDLM devices
Block logical device files for HDLM devices are created in /dev/dsk.
Character logical device files for HDLM devices are created in /dev/rdsk.
Distributing a Load Using Load Balancing
When the system contains multiple paths to a single LU, HDLM can distribute
the load across the paths by using multiple paths to transfer the I/O data.
This function is called load balancing, and it prevents a single, heavily loaded
path from affecting the performance of the entire system.
Note that some I/O operations managed by HDLM can be distributed to each
path, while others cannot. Therefore, even though load balancing function is
used, I/O operations might not be equally allocated to each path.
Figure 2-5 Flow of I/O Data When the Load Balancing Function Is Not Used on
page 2-11 shows the flow of I/O data when the load balancing function is
not used. Figure 2-6 Flow of I/O Data When the Load Balancing Function Is
Used on page 2-12 shows the flow of I/O data when the load balancing
function is used. Both figures show an example of an I/O being issued for the
same LU from multiple applications.
2-10
HDLM Functions
Hitachi Dynamic Link Manager User Guide for Solaris ®