Installation guide

to that HSC controller are inaccessible. Attempts to access those disks will
cause the accessing system to hang until the HSC reboots completely. Refer
to your processor hardware documentation for explicit instructions on
booting an HSC disk.
C.5 Sharing Disk and Tape Units Among Several Hosts
Although an HSC can be shared among several hosts, there is no software
interlocking mechanism to prevent concurrent write operations to the same
partition by multiple Tru64 UNIX systems. The following restrictions must
be observed:
• Only multiple readers can share a disk unit; writable file systems
cannot be shared.
• If a disk will be shared, it should be hardware write protected.
• Each host must mount the file systems to be accessed with the
read-only (
-r) option to the mount command.
• Only a single host can mount a disk that contains writable file systems.
• Use the Network File System (NFS) if multiple writers need to share
partitions.
You should coordinate disk unit ownership among the hosts on the CI bus,
for example, assign a range of disk unit numbers to each host. The HSC
controller can also be directed to limit disk access to an exclusive host
system. This limitation protects the disk from accidental access by another
host on the CI bus. For more information, see the radisk
(8) reference
page, in particular the −e and −n options.
Tape drives that are attached to an HSC controller can be shared. This
feature is recommended and provides greater use of tape drives. Be aware
that the access mechanism provides serial sharing of the drives, not
simultaneous access.
Support of the CI and HSC Hardware C–3