RemoteSHADOW® V1.5 for Tru64 UNIX:
RemoteSHADOW (RSO
TM) combines local and remote shadowing capabilities
to provide intra-day recovery of your critical business data in the event of a disk
drive, controller, system or data-center failure. RSO, which is application transparent,
shadows your data to a contingency system which may be in an entirely different
location many miles from your primary data center. RemoteSHADOW does not have a
distance limitation. Your data is instantly available at the contingency site in
the event you lose your production systems and/or site.
A shadow set consists of up to ten members. A member is any local or remote disk
device partition. All user write I/O operations to the shadow set are directed to
all available members within the set. Each member has an associated read cost value,
which the user can change. Read operations result in the data being read from the
fastest device.
RemoteSHADOW offers automatic and transparent rollover on a member failure within
a 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 application. When a hardware error is detected on a shadow set device, that
device is "removed" from the set and the failure is logged to a journal.
RemoteSHADOW offers users the ability to dynamically create and/or delete shadow
sets and to add, modify, and/or remove a member within a set with no interruption
or loss of service. When you want to add a member to a shadow set, RemoteSHADOW
offers an optimized, on-line-disk copy facility to ensure that all volumes within
the set reflect the same data. This copy facility is known as a Volume Copy. To
add a member to a set, the size of the device partition you wish to add must be
of equal or greater storage capacity than that of the original device partition
to be shadowed.
RSO also provides a Hold/Release command mechanism, enabling users to access the
remote members of a set for read-only purposes. The user instructs RemoteSHADOW
to hold I/Os designated for the remote device while on hold. When the user is finished
using the remote device, the release command will apply the held I/Os and bring
the remote device back into the shadow set.
Shadowing Operations:
Figure 1: Sample Shadow Set
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Figure 2: RemoteSHADOW Set
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Local shadowing involves shadowing data to locally attached devices.
Figure 1 illustrates a sample shadow set. A pseudo device named /dev/rsset0g represents
a two local member set consisting of /dev/rz5g and /dev/rz3h. All I/Os directed
to /dev/rsset0g are shadowed to both members. If one of the member fails, RemoteSHADOW
will drop the member from the set and continue operating with the remaining member.
RemoteSHADOW:
RemoteSHADOW allows you to add remote members to a set. On the production system,
the RemoteSHADOW Master Component must be installed and running. To make a member
accessible to a production system on the network, the RemoteSHADOW Remote Daemon
must be installed and running on the contingency (or remote) system.
Figure 2 shows there are three members in the shadow set (/dev/rsset0g).
System A has two local members and one remote member in its set. System A should
have the Master Component of RemoteSHADOW installed and running. System B should
have the Remote Component of RemoteSHADOW installed and running.
Synchronization Tolerance:
Synchronization Tolerance (or Sync Tolerance) is an ASCI created concept in which
business managers can balance production system performance and bandwidth requirements
with intra-day recovery needs. Sync Tolerance is expressed in seconds. When a RemoteSHADOW
set member specifies a zero (0) sync tolerance, all Write operations must complete
on all members before completing the I/O. In this manner the remote member is in-sync
with the set at all times. Specifying a greater than zero (0) sync tolerance value
means that insufficient network bandwidth should not impact the local system. Thus,
the remote member is to be updated asynchronously after the local system. Regardless,
RemoteSHADOW will always try to keep the remote member in-sync whenever possible.
The sync-tolerance value for a remote member is specified by the user. For example,
a sync-tolerance value of 600 seconds would allow the remote member to lag behind
the local member up to a maximum of ten (10) minutes.
Network Restart:
RemoteSHADOW provides a communications-network-restart feature that allows a recovery
from temporary-network failures without the need for a remote volume-copy. The network
timeout value (in seconds) is user configurable.
Utility Program:
The RemoteSHADOW Tools program is a user-friendly utility program used to administer
the system. The utility program lets you add/delete shadow sets and/or add/modify/remove
members from sets. The utility program can be run as a command without user interaction
or as a mini-shell that requires user interaction.
Monitor Program:
The RemoteSHADOW Monitor program lets you monitor the system and/or their members
in real-time. The program provides real-time data of the I/O's being performed by
the RemoteSHADOW members.
Configuration Program:
The RemoteSHADOW Configuration (RSC) program automates the initial setup of RemoteSHADOW.
RSC makes all the necessary changes to the system startup files necessary to properly
run RemoteSHADOW at boot-up time. RSC also lets the user decide which sets to automatically
mount at boot-up and (in the case of some shadow sets) where to mount them on the
file system.
Logging:
RemoteSHADOW logs all important messages and errors to log files. Depending on the
criticality of the error message, the message may also be mailed to "root" and/or
logged to the console for immediate attention.
Supported Environments:
RemoteSHADOW supports the UFS file-system, AdvFS file-system, Synchronous I/Os,
Asynchronous I/Os, and Logical Storage Manager (LSM). RemoteSHADOW supports character/raw
mode and block mode access. RemoteSHADOW will run on all SMP (Symmetric Multi-Processor)
machines and supports disks of any size, density, and make. RemoteSHADOW also supports
database systems such as Oracle and Sybase.
Minimum Hardware Supported:
RemoteSHADOW is warranted for use with all Digital supported buses, used in conjunction
with Digital-supplied device drivers. RemoteSHADOW also works with all third-party
controllers and disk drives that use unmodified, Digital disk-device drivers.
Prerequisite Software:
RemoteSHADOW runs on any Alpha processor, running Tru64 UNIX V4.0 or later.
RemoteSHADOW requires TCP/IP for shadowing data remotely.
The nroff product must also be installed on the system for using the online help
which is provided in the form of man pages. The nroff product is part of the "Text
Processing: Doc. Preparation Tools" subset provided with Tru64 UNIX.
Software Installation:
Installation of the RemoteSHADOW product is subject to the terms of the ASCI Standard
Software Product License Agreement. RemoteSHADOW is designed to be installed by
the System Administrator. An optional installation script is provided to automate
the installation and setup procedures.
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
technical assistance, remedial telephone support, and product upgrades.
Maintenance Information:
After the initial product warranty expires, ASCI offers an annual support plan.
This includes technical assistance, remedial telephone support, product upgrades,
and enhancements, as they become available. The annual customer support plan is
separately priced.
Ordering Information:
This software is Licensed in several different ways. The Full-Function license supports
both the local and remote shadow. The Local Only Shadow license supports local shadowing
on a single system.
This software is licensed using Digital's Licensing Management Facility (LMF). A
Product Authorization Key (PAK) is required for each system prior to product installation
and execution.
RemoteSHADOW consists of a CD-ROM distribution of software, User's Manual, Software
Product License Agreement, Software Product Description, and ASCI Product Authorization
Key.
SHA_550_LIC-Local Only SHADOW License and Documentation
SHA_551_LIC-License and Documentation
SHA_550_RTC-Local Only SHADOW Right to Copy License
SHA_551_RTC-Right to Copy License
AD_550_SHA-Users Guide
