HP StoreEver Tape Libraries Failover User Guide (5697-3323, June 2014)

10 Installing and using HP-UX advanced path failover drivers
Advanced path failover for HP-UX is implemented by updating HP-UX drivers to support advanced
path failover with the LTO-6 tape drives. The drivers function as both failover and non-failover
drivers.
The updated drivers are:
• HP-UX tape driver (estape) — used for data path failover
• HP-UX media changer driver (eschgr) — used for control path failover
• HP-UX SCSI stack driver (esctl) — used for data path and control path failover
During the device open, the device driver checks to see whether the device is capable and enabled
for advanced path failover. If so, the device driver opens a failover session and continues with
further device operations. Otherwise, the driver uses the non-failover driver code. Note that until
the device is opened for the first time, the drivers do not know whether the device is capable of
advanced path failover or not.
HP-UX 11i v3 performs automatic load balancing and will open new tape drive connections using
the best available path to spread the load across all available paths. In HP-UX 11i v3, the default
load balance policy for tape drives and libraries is the “Path-lockdown” policy. With this policy,
the host determines a path for sending I/O requests to the device when the device is opened for
the first time and this path remains fixed. Without the advanced path failover feature installed, if
this path fails, a new path is only chosen when the device is next opened. With the advanced path
failover feature, the best path will be chosen as the lockdown path. If this path fails, the driver will
automatically fail over to the next available best path, which becomes the new lockdown path for
all further I/O requests.
For additional information see the following man pages: scsimgr(1M), ioscan(1M), mknod(2),
mksf(1M), rmsf(1M).
Installing advanced path failover drivers
The patch catalog is available at http://patch-hub.corp.hp.com/wtec/catalog/. To locate the
patches in the catalog, search for estape, eschgr, and esctl, or the patch number and then
look at the Prepby field to see if there is a superseding patch.
To install the advanced path failover drivers, use the standard HP-UX kernel patch installation
process to install the following patches on the HP-UX host servers running HP-UX 11i v3:
• HP-UX Tape driver patch (estape) - PHKL_43680 or superseding patch
• HP-UX Media changer driver patch (eschgr) - PHKL_43681 or superseding patch
• HP-UX SCSI stack (Mass storage stack) driver patch (esctl) – PHKL_43819 or superseding
patch
The server will automatically reboot as part of the installation process.
Commands for viewing tape and library devices connected to a system
You can use ioscan to view the tape and library (media changer) devices connected to the HP-UX
host. The device special file (DSF) is listed as the last item in the description as shown in bold type.
Installing advanced path failover drivers 47