Overview: The Next Generation Mass Storage Stack (September 2009)

Several new command options provide performance information:
scsimgr get_stat
Displays mass storage statistics, either at a global level or for a particular LUN,
target, or controller.
glance –U
Displays HBA port-level statistics. The motif version of glance (gpm) has a new
IO by HBA report under the Disk details menu.
sar –H
Displays HBA port-level activity.
sar -L
Displays separate activity for each lunpath.
sar -t
Displays tape activity.
sar -R
Displays disk reads per second and disk writes per second as separate
columns.
For additional information on I/O performance in HP-UX 11i v3, see the HP-UX 11i v3 Mass Storage I/O
Performance Improvements white paper in For more
information.
Introduction to the Agile View
This section shows how the agile view appears as the DSF names and hardware paths differ from previous
releases. The DSFs, paths, and ioscan output for a sample system are displayed with an explanation of how they
change for the next generation mass storage stack. After this comparison, additional sections provide more
detailed information about the hardware paths and DSF types.
The example configuration has three HBAs: one parallel SCSI HBA and two Fibre Channel HBAs connected to a
disk array. There are four disks on the example system, two on parallel SCSI and two in the disk array. One of the
Fibre Channel disks is multi-pathed and is connected to both Fibre Channel cards.
Note: The configuration diagrams and ioscan listings have been edited for readability; entries for non-mass
storage devices have been omitted.
Legacy View
On releases prior to HP-UX 11i v3, the disks on the example configuration included the hardware paths, driver
names, and DSFs shown in Figure 1. This environment is referred to as the legacy view.
In Figure 1, the HBAs are on the left side. The disks are shown on the right side with their associated DSFs inside.
Connections from the HBAs to the disks are shown as a solid line. Above the connection is the hardware path
shown by the I/O commands such as ioscan.
Following are important concepts displayed in Figure 1:
• Parallel SCSI disks use a SCSI-2 addressing paradigm, which supports up to eight LUNs per target and
16 targets per controller. Thus, addressing beyond the HBA consists of a target port ID and a LUN ID.
These are directly incorporated into the hardware path for the disk.
• Fibre Channel disks use SCSI-3 addressing, which supports a larger addressing model in which the
number of target paths per controller or LUN paths per target are limited only by device, controller, or
transport protocol addressing restrictions. The addressing beyond the HBA contains the worldwide port
name and LUN ID. However, in the legacy view, the Fibre Channel hardware path uses the SCSI-2
addressing model by creating virtual controllers, virtual targets, and virtual LUNs.
• The DSF name for each disk contains hardware path information. The multi-pathed disk has two different
DSFs, one for each hardware path. There is no indication that both DSFs refer to the same disk.
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