HP-UX 11i v3 Mass Storage I/O Performance Improvements

• Native Multi-Pathing support. LVM is designed to work seamlessly with the native multi-pathing,
enabling all of the corresponding performance benefits without having to be concerned with the
specifics of LUN paths.
• Fast vgscan. With the new -k option, vgscan can recover activated volume groups in
/etc/lvmtab quickly (in seconds), even if the system has large number of LVM disks configured.
• Striping + mirroring support. Previously a logical volume could be mirrored or striped but not both.
On HP-UX 11i v3 LVM introduces support for striped and mirrored logical volumes at a smaller
granularity than the extent size (allowing stripe sizes as small as 4 KB), offering increased
opportunities for better performance.
For additional information on each of these improvements, see the LVM New Features in HP-UX 11i
v3 white paper.
Async Disk Driver Improvements
The Async Disk driver has been enhanced in HP-UX 11i v3 to provide the following:
• Dynamic scaling — The max_async_ports tunable, which specifies the maximum number of
open asyncdsk ports, has been enhanced to be dynamically changeable in HP-UX 11i v3. In prior
releases a reboot was required to change the number of ports, but in 11i v3 it can be changed with
the kctune command at any time, even while the Async Disk driver is in use. This allows the
system administrator to much more readily tune or re-tune the Async Disk driver as needed.
• More efficient, just-in-time, port allocation: in prior releases all ports up to the maximum specified
by the max_async_ports tunable were pre-allocated and the required memory consumed
whether the port was used or not. In HP-UX 11i v3 memory is not consumed until a port is actually
opened.
• Higher max_async_ports default: the default value for the tunable has been increased from 50
to 4096, making it much less likely that the administrator will need to adjust the value. This much
higher default can be provided on HP-UX 11i v3 without wasting memory due to the more efficient
port allocation described previously.
• No longer need to set 0x100 in minor number: HP-UX 11i v3 has been enhanced to no longer
require the setting of 0x100 in the Async Disk driver minor number as had been required in
previous releases to avoid long memory lock-down times.
11