RemoteSHADOW® for OpenVMS:
The Disk Mirroring system for OpenVMS allows a VMS System Manager to maintain redundant
databases for the survival of media failures.
A shadow set consists of a master-disk device and one or more members. User applications
issue I/O operations to the master disk, which is a Files-11-mounted device. Write
operations are performed for all available members within the set and Read operations
are balanced. An additional feature allows a user to specify a preferred drive for
reading.
SHADOW offers an automatic and transparent rollover on a member failure within the
shadow set. As long as a single member within the set remains available for I/O
operations, RemoteSHADOW does not pass back any notification of the failure to the
user program. All modifications to shadow-set status are logged to the operator
console and journaled to a disk file for audit purposes. When a hardware error is
detected on a set, that device is "removed".
SHADOW offers users the ability to create and/or delete shadow sets and to add,
modify, and/or remove a member with no interruption or loss of service. When you
want to add a member, RemoteSHADOW offers an optimized, on-line-disk copy facility
to ensure that all volumes reflect the same data. This on-line copy is further optimized
by selectively copying only those sectors which have been allocated under the Files-11
structure.
The user-interface program is invoked in the DCL-command style with qualifiers and
parameters for program input. RemoteSHADOW uses the normal VMS privileges required
for manipulating disk volumes.
The MONITOR program uses a windows-oriented approach to display shadow-set information
on one or more nodes within the DECnet network. MONITOR also allows the entry of
commands for your additional convenience.
FileSHADOW Option:
The FileSHADOW Option provides the added capabilities of: Shadowing selected critical
files, and Shadowing dissimilar (heterogenous) disks.
Shadowing selected files can significantly reduce the overall disk storage requirements
which other systems can consume. A performance enhancement can also be realized
since read I/O's are balanced and only the critical files you designate have their
write I/O's mirrored. To shadow one or more critical files, you create a virtual
disk of specified size, into which you place your files. This virtual disk can then
be shadowed to either a real physical disk or another virtual disk. Shadowing a
physical disk to a virtual disk is the underlying concept behind dissimilar support.
The real disk may be an RZ26 while the virtual disk resides on the unused portion
of an RZ28. This allows an RZ26 to be shadowed to a portion of an RZ28, and the
remaining free space can be used for any other purpose.
The FileSHADOW option is a layered product of SHADOW and is separately priced.
RemoteSHADOW Option:
With the RemoteSHADOW Option(RSO), the strategy for coping with media failures can
be expanded to include local-site failures. The RemoteSHADOW Option provides the
capability for continuing access to and availability of your data, even when your
local-computer site is down. This option means that your high-availability applications
can continue to operate from a contingency site using todays data. The RemoteSHADOW
Option allows a VMS System Manager to designate one or more shadow-set members as
remote volumes. RSO uses a high-speed network for remote communications and supports
the concept of out-of-sync tolerance. When a shadow set specifies no out-of-sync
tolerance, all Write operations must complete on local and remote systems together.
In this manner both the local and remote systems are in synchronization. When the
disk I/O traffic and rates exceed the network-communications throughput, a set may
specify an out-of-sync tolerance. Specified in time (seconds), an out-of-sync tolerance
means that insufficient network bandwidth should not impact the local system and
that the remote system is to be updated asynchronously after the local system. Thus,
the local and remote systems can be out of synchronization. The maximum out-of-sync
tolerance is user-specifiable. For example, 600 seconds would allow a remote system
to be a maximum of ten (10) minutes behind a local system. RSO does endeavor to
stay in-sync as much as is possible. All Read operations are performed from faster
local drives, regardless of out-of-sync tolerance.
The RemoteSHADOW Option also provides a communications-network-restart feature that
allows a recovery from temporary-network failures without the need for a volume
catchup.
For improved-network utilization, RSO provides a data-compression feature that,
depending upon user data, can significantly reduce the raw amount of transmitted
data. RSO also supports a network-data-encryption feature that, when enabled, encrypts
all transmitted and/or received data. This feature ensures that your proprietary
and sensitive data never becomes viewable over a communication line.
The RemoteSHADOW option is a layered product of SHADOW and is separately priced.
(The FileSHADOW Option is included with the RemoteSHADOW Option).
Minimum Hardware Supported:
This product requires a valid OpenVMS configuration. It is warranted for use with
Digital's MASSBUS, UNIBUS, QBUS, DSA, DSSI, BI, XMI and SCSI disks, used in conjunction
with any Digital-disk controller.
SHADOW fully supports the VMScluster environment and also works with all third-party
controllers and disk drives that use unmodified, Digital disk-device drivers.
Prerequisite Software:
SHADOW V2.6 runs on any OpenVMS processor, using VMS VAX Version 5.5-2 or later,
or OpenVMS Alpha V6.1 or later. For execution within a VMScluster, ASCI highly recommends
an OpenVMS DECnet Full-Function license.
The RemoteSHADOW Option supports OpenVMS DECnet and/or TCP-IP.
Optional Software:
The FileSHADOW Option as described in this Software Product Description.
The RemoteSHADOW Option as described in this Software Product Description.
VIRTUOSO Virtual Disk and Disk Caching system can be combined with SHADOW to allow
the shadowing of partial, rather than full volumes. VIRTUOSO also provides Data
Caching, Disk Striping, Encryption and other features that improve the performance,
reliability, and security of disk data.
Software Installation:
Installation of this product is subject to the terms of the ASCI Standard Software
Product License Agreement. SHADOW is designed to be Customer installable and uses
Digital's VMSINSTAL facility.
Warranty Information:
This software is sold through ASCI's Software Product License Agreement which warrants
the product for ninety (90) days from the date of purchase. Warranty services include
telephone-remedial support and product upgrades.
Customer Support Information:
After the initial product warranty expires, ASCI offers a twelve-month customer
support plan. This includes remedial support, product upgrades as they become available.
The annual customer support plan is separately priced.
Ordering Information:
ASCI normally distributes all material via CD-ROM. However, ASCI honors requests
for other magnetic media for a minimal charge, but you must indicate these in your
letter and/or purchase order. The current prices are available upon request. Multi-CPU
and Educational-Institution discounts are available.
This software is licensed under Digital's License Management Facility (LMF). A Product
Authorization Key (PAK) is required prior to product installation and execution.
SHADOW consists of a CD-ROM distribution of software (1), User's Manual (1), Software
Product License Agreement, Software Product Description, and Warranty Registration
Certificate.
The RemoteSHADOW Option consists of a CD-ROM distribution of software (1) and Addendum
(1).
SHA_150_LIC-License and Distribution Media
SHA_151_LIC-RemoteSHADOW Option License and Distribution Media
SHA_152_LIC-FileSHADOW Option License and Distribution Media
SHA_150_RTC-SHADOW-Right-to-Copy License
SHA_151_RTC-RemoteSHADOW Option Right-to-Copy License
SHA_152_RTC-FileSHADOW Option Right-to-Copy License
AD_150_SHA-User's Guide
