An e-mail server can stop delivering e-mail for several reasons: a loss of Internet connectivity, a hardware failure, an operating
system crash, an e-mail server software crash, or a corruption of the database that stores the messages. The traditional backup-and-restore
process can take hours to resurrect a server, and any mail that comes in while the server is down will be lost. As a result,
not surprisingly, many organizations demand CDP (continuous data protection) for e-mail.
The options start with Microsoft’s own Windows Server 2003 Clustering Services and extend to a range of third-party fail-over
and high-availability solutions. Windows clustering allows Exchange Server 2003 to be set up in either an active/passive cluster
or a cluster of multiple servers with one standby server. This is highly effective in ensuring uptime, but it is complex to
set up, requires extra hardware and licenses, and does not protect against data loss or database corruption (see “Windows clustering a costly option for Exchange fail-over”).
The solutions reviewed here can cope with almost any Exchange-related mishap, except Internet failures, and they do so more
simply, at lower costs, and with additional flexibility or protection compared with the native Exchange cluster. Two solutions,
Neverfail for Exchange and SteelEye LifeKeeper, bring true fail-over to an entire Exchange server. Two others, Cemaphore Systems
MailShadow and Quest Availability Manager, protect individual mailboxes on one or more Exchange servers. And one, Lucid8 DigiVault,
provides backup of data stores that can be restored to a secondary Exchange server. For maximum protection, administrators
might choose to implement a fail-over system plus the CDP that DigiVault provides. (Yet another alternative is a high-availability
Exchange appliance from Azaleos or Teneros. These solutions are installed on your premises but managed and monitored off-site.
See our review "High-availability Exchange made easy").
Each product takes a different approach to protecting Exchange and offers different advantages. Some of the differentiators
are, for example, whether an Exchange server license is required for the backup server, whether more than one server can be
protected by a single backup server, whether an agent is required on each Exchange server, and whether replication over WAN
links is supported.
The test setup for each product consisted of a domain controller (Active Directory), two Exchange servers (the primary and
secondary), and any additional servers as required by the individual product. I set up replication of the primary Exchange
server to the secondary and then simulated failures by unplugging the network cable from the primary, stopping the Exchange
Information Store service, and dismounting the drive the information store was running on, while monitoring incoming messages
and simulating traffic using LoadSim. I observed the Outlook client experience when the primary server failed, as well as
the time required to fail over to the secondary server.
Neverfailfor Exchange
Neverfail is a true, automatic, active/passive fail-over solution. It uses primary and secondary Exchange servers linked via
crossover cable to maintain a heartbeat connection and perform data synchronization. If the primary server experiences a hardware
or software failure, the secondary server assumes its IP address and hostname and resumes operation. I tested Neverfail for
Exchange 5.0. Neverfail Group offers a variety of application modules other than Exchange, including IBM Lotus Domino, Microsoft
File Server, Oracle Database, SharePoint, and SQL Server.
Neverfail provides functionality comparable with that of Windows Clustering, and because it doesn’t require Windows Server
2003 Enterprise or DataCenter and Exchange Enterprise Edition, the overall cost is comparable. Neverfail goes beyond Windows
Clustering in providing easier setup, great management, and an intelligent analysis and monitoring tool that can find and
resolve problems on the Exchange server before they cause failures. Further, as opposed to Windows Clustering, Neverfail doesn’t
require the hardware of the primary and secondary systems to be identical.
Cost: Pricing begins at $7,600 per pair of servers; Neverfail charges a 20 percent annual maintenance fee
Platforms: Windows 2000 Server or Windows Server 2003; Exchange 2000 Server or Exchange Server 2003
Bottom Line: Neverfail offers true, automatic fail-over with minimal impact on users and without the drawbacks of Windows Clustering such
as the requirement for identical hardware and advanced server versions. It is fairly simple to install and manage. As opposed
to Windows Clustering, it works only in pairs of servers.
Cost: Price is $3,280 per server; annual support costs $820 per server
Platforms: Windows 2000 Server or Windows Server 2003; Exchange 2000 Server or Exchange Server 2003
Bottom Line: SteelEye LifeKeeper offers a true fail-over cluster with additional options for remote asynchronous replication and one-to-many
replication. Initial configuration can be complex, mostly due to all the options. One secondary server can support more than
one primary Exchange server.
Cost: $50 per year for every mailbox to be protected; volume discounts available; MailShadow server license does not carry a separate
charge
Platforms: Windows Server 2003 and Exchange Server 2003
Bottom Line: MailShadow offers excellent protection of individual mailboxes, easy setup, and agentless operation. However, fail-over from
primary to backup server is manual. The agentless system will appeal to some administrators, whereas others will wish for
an automatic fail-over process.
Cost: $8 per mailbox per year; Quest Availability Suite for Exchange, which also includes Spotlight on Exchange, starts at $10 per
managed mailbox.
Platforms: Windows 2000 Server or Windows Server 2003; Exchange 2000 Server or Exchange Server 2003
Bottom Line: Quest Availability Manager for Exchange offers good protection including automatic fail-over and the ability to designate
which users are protected. Administration is easy, and integration with Quest’s other tools for Exchange is excellent, as
is the pricing.
Cost: Licensing on a per-server basis, with pricing based on the number of mailboxes, starting at $695 for 25 mailboxes
Platforms: Windows 2000 Server and Windows Server 2003; Exchange 5.5, Exchange 2000, and Exchange 2003
Bottom Line: DigiVault brings continuous data protection to Exchange, offering easy setup, a simple interface, and high-speed restores.
Mailbox stores can be restored to different servers in the case of hardware failure or an auditing requirement.
» Database vendors add Google's MapReduce
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» Network management: Tips for managing costs
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SLM AND BSM: THE FUTURE OF IT MANAGEMENT. ARE YOU READY? Driven by globalization and competition, businesses increasingly look to IT to enable them to quickly adapt to changing business conditions, speed the delivery of products and services, and automate processes, all at lower costs. Additionally, service quality and positive customer experiences are also top priorities. The only way to meet these expectations is to cohesively manage
IT-across the enterprise-from a business service point-of-view.
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