If you don't consider disaster planning and availability part of your
network management strategy, consider Stratus Computer's findings from a recent
survey of Fortune 1000 companies. In 1992 (the last year such research data was
available), computer downtime cost US businesses more than $3.8 billion in lost
revenue and worker productivity. This downtime equals an average hourly revenue
loss of $78,000 and approximately 38 million worker hours annually, or $444
million in wages.
A sudden loss of a mission-critical server can be financially disastrous.
In most companies, just the downtime before recovery can be too costly. Still
not convinced? According to "Down But Not Out" (HP Professional,
September 1994), "The average company loses two to three percent of its
gross sales within 10 days after losing its data processing, and critical
business functions cannot continue for more than 4.8 days without a recovery
plan in progress. Half of the companies that do not restore their data center to
operation within 10 business days never fully recover. Ninety-three percent of
the companies lacking a recovery plan are out of business within five years of a
major disaster."
Despite these claims, few companies plan ways to prevent or mitigate losses.
To protect the bottom line, companies need to evaluate potential losses and
implement an appropriate availability scheme for their network.
A good starting point is to review the availability mechanisms that Windows
NT Server supports. These mechanisms include data backup, uninterruptible power
supplies (UPSs), and redundant systems. With an understanding of the options,
companies can make informed decisions about implementing the appropriate levels
of protection for their LAN and WAN and be better prepared for the next level of
availability--ensuring server availability with server redundancy.
LAN Availability
Downtime can result from disasters such as fires, floods, power failures,
and--let's face it--users. Users frequently (yet accidentally) delete critical
files or stumble onto control-key combinations that can restructure databases
and wreak havoc throughout a company. So when planning a network, you need to
consider availability, backup, and disaster recovery.
Most network administrators implement availability by a mirroring of the
primary system. This redundant system eliminates single points of failure.
Fortunately, NT Server comes with support for tape backup, UPS, and redundant
systems.
Critical Data and Programs
Data backup is at the forefront of availability. The backup process copies
important information onto magnetic tape or disks. Without backups, vital data,
complex application and network configurations, customized setups, and user
passwords and IDs are difficult and expensive--perhaps even impossible--to
re-create. Backing up information is also important because of its changing
nature. Compaq reports that as much as 40% of its company data changes every
month.
To restore a system after a disaster, you need to back up all data and
programs and determine whether certain users or groups have special backup
needs. For example, an accounting group may require data backups beyond the
regularly scheduled full-system backups. For information on NT-native backup
programs, see Bob Chronister, "System and Enterprise-wide Backup Software,"
Windows NT Magazine, April 1996.
UPSs
Most systems improve OS performance by writing changes to RAM before writing
them to disk (write-back caching). When a power interruption turns off or resets
a computer, you can lose cached information and potentially corrupt data.
Because the server processes most data on the network, any power fluctuations
can adversely affect data flow to and from client workstations.
Most system administrators equip critical servers with UPSs in case of a
power failure. But don't overlook key network connection points such as main
servers and LAN/WAN peripherals (routers, bridges, hubs, and concentrators).
Site-to-site and wide-area networks are susceptible at these points, so use UPSs
to maintain data flow and processing stability among servers.
What about client workstations? In a peer-to-peer network, any workstation
can be the server to any other workstation on the network. Peer-to-peer activity
greatly increases the data flow on the network to each workstation, but makes
them susceptible to brownouts and blackouts. So, you need UPSs at client
workstations. This way, if you lose power, you have time to save active files
and do an orderly shutdown. For more information, see Larry McClain, "Roundup
of UPS Products for Windows NT," Windows NT Magazine, November
1995.