HP Archive Backup System for OpenVMS Guide to Operations

ABS/MDMS Support for Fibre Channel
E.3 FC connected tape devices, medium changers (robots) and SMS Products
This introduces the issue of different servers writing over each other or intertwined writes if the
access to the device is not synchronized. Currently, there is no OpenVMS resource lock mechanism
that spans the domain of the SAN and all of the possibly heterogeneous systems connected
to it.
The OpenVMS operating system neither supports sharing of single devices across different operating
systems nor between OpenVMS nodes not within the same VMScluster. The HSG access
path setting for each device and/or FC switch zoning can be used to ensure that each HSG storage
device is accessible to only one cluster or one non-clustered system.
E.3 FC connected tape devices, medium changers (robots) and
SMS Products
E.3.0.1
The SCSI tapes and libraries are connected to the Fibre Channel by a Fibre-to-SCSI bridge
known as the Modular Data Router (MDR). Open VMS currently support MDR connected to a
switch and configured in SCSI Command Controller (SCC) mode. Network Storage Router
(NSR) M2402 by HP is a key component in a complete data protection solution.
It allows multiple host servers to communicate with a SCSI tape device over a Fibre Channel
link making backup speeds five times faster. HSM has been tested and qualified with Network
Storage Router (NSR) M2402.
Tape and medium changer devices are automatically named and configured using the SYSMAN
IO FIND and IO AUTOCONFIGURE commands as described in Guidelines for OpenVMS
Cluster Configurations manual (April 2001) Manual. Fibre Channel tape names are in the form
$2$MGAn. The letter for the controller is always A, allocation class is set as 2. The device mnemonic
for tapes is MG and GG for medium changers. The device unit n is automatically generated
by OpenVMS. Tape and medium changer names are automatically kept consistent within a
single OpenVMS Cluster system. Once any node in the cluster names a tape device, all other
nodes in the cluster automatically choose the same name for that device. The chosen device
name remains the same through all subsequent reboot operations in the cluster.
If multiple non-clustered Alpha systems on a SAN need to access the same tape device on the
Fibre Channel, then the application software must provide synchronized device access.
HP Media Device Management System (MDMS) for OpenVMS:
E.3.0.2
MDMS V3.2 and above supports sharing of tape device and juke box (media changer) across
non-clustered nodes as long all the nodes are in a single MDMS domain and use MDMS to allocate
the drive. You must specify all the nodes or groups of nodes who can directly access the
Drive or Jukebox (through FC). The accessibility attribute is defined by using the /NODE or
/GROUP qualifiers in the DCL command set for MDMS or by using the MDMS GUI. MDMS
presently supports sharing of a tape device across a maximum of 32 clusters.
Due to the VMS algorithm of discovery and naming the device, it may happen that the same
tape, media changer device may be visible as different device name on nodes in different clusters.
This would introduce the problem of nodes, that see the device with a different name than
that specified in the DEVICE field of MDMS drive database, not able to access the device. One
way of configuring such FC served devices is by manually editing the SYS$SYS-
TEM:SYS$DEVICES.DAT file on the clusters sharing the device so as to make the device name
the same. Please refer OpenVMS Cluster Configuration Manual for details.
HP Archive Backup System (ABS) for OpenVMS:
ABS uses MDMS to allocate tape devices, hence ABS supports the entire configuration supported
by MDMS. ABS V3.2 and above provides for FC connected tape storage support.
E–2 ABS/MDMS Support for Fibre Channel