Alternate Links (PVLinks): In HP-UX 11i v3, management of multi-pathed devices is available
outside of LVM using the next generation mass storage stack. By default,
the next generation mass storage stack distributes I/O requests across
all available paths to a multi-pathed disk, even when using legacy
device special files. Using LVM with persistent or legacy device special
files may cause I/O requests to be sent across alternate links, even
if the links are not configured as PVLinks; this should not introduce
any errors, but it does differ from PVLink behavior in previous releases.
HP recommends converting volume groups with multi-pathed
disks to persistent device special files and native multi-pathing,
as described in the migration white paper in “Related Documentation”.
However, if you want backward-compatible PVLink
behavior, you must use legacy device special files for physical volumes,
and disable the mass storage stack multi-pathing for those physical
volumes. To disable multi-pathing on legacy device special files,
use the scsimgr command to configure a global device
tunable called leg_mpath_enable.
For each multi-pathed disk, enter the following
command:
# scsimgr save_attr -D /dev/rdisk/diskn -a leg_mpath_enable=false |
Alternatively, you can disable multi-pathing for
all legacy device files with this command:
# scsimgr save_attr -a leg_mpath_enable=false |
Note that this has no effect on multi-pathing
through persistent device special files. For more information, see scsimgr(1M).
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