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IT Challenges in the Business Continuity Market

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									IT Challenges in the Business Continuity Market


                                      1601 Trapelo Road
                                     Waltham, MA 02451

  Introduction __________________________________________________ 1
  Terminology __________________________________________________ 2
  IT Challenges in the Business Continuity Market _____________________ 3
  Overcoming the Hurdles with WANSync ____________________________ 6
  WANSync Products ___________________________________________ 17
  Summary ___________________________________________________ 17

Page iii           XOsoft White Paper – IT Challenges in the Business Continuity Market
       In a world that relentlessly conducts business around the clock, information system
       managers must be prepared to ensure continuous access to business-critical
       applications and data. Business Continuity is a relatively new term that is often
       thought of as another way to say "disaster recovery", but in reality means much
       more. Business Continuity represents the seamless, uninterrupted provision of
       operations and services.
       An application or service that is “continuously available” must be able to tolerate
       virtually any cause of failure within the system. Geological events, severe weather,
       physical and cyber terrorism, strained or underdeveloped infrastructures – all may
       cause failure at a data center, regardless of its design. The only viable solution to
       these potential problems is to separate the data centers sufficiently (100 kilometers
       or more), as to ensure that a disaster at the primary location does not directly affect
       the secondary location(s). To ensure further protection, the continuity infrastructure
       must be designed to perform automatic failover in the event of disaster.
       According to the market research firm Ovum, companies once exhibiting
       reluctance in establishing a central control facility for all their mission-critical
       applications will be proactively reviewing their options. There will be an increase
       in demand for linking these facilities together through telecom networks and for
       guaranteed data synchronization. The IT trend will be towards more data centers,
       backup and data continuity systems. This brings into focus the increasing
       importance of data distribution and synchronization, generally referred to as
       “replication”, over the Wide Area Network (WAN).
       This white paper will present the challenges that IT professionals face when
       implementing a geographically distributed data configuration in their network, and
       the features that a comprehensive replication solution must implement to answer
       these challenges.

XOsoft White Paper – IT Challenges in the Business Continuity Market               Page 1
First, we will define some of the terms used throughout this document.

Application         A computer in a client/server environment that performs the business
Server              logic (data processing). The application server is part of a three-tier
                    application, consisting of a graphical user interface (GUI) server, an
                    application (business logic) server, and a database and transaction
Database Server     A computer dedicated to database storage and retrieval. It holds the
                    database management system (DBMS) and the databases. Upon
                    request from client computers, the database server searches the
                    database for selected records and returns them over the network.
File Server        A computer attached to a network that stores the programs and data
                   files shared by large number of users. It acts like a remote disk drive.
                    The difference between a file server and an application server is that
                    the file server stores the programs and data, while the application
                   server runs the programs and processes the data.
Journaling         Keeping track of events by recording them in a journal, or log.
Master             The host computer on which original files reside and on which
                   replication events start.
Production          See Master.
Recovery            The combination of manual and machine procedures that can restore
                    lost data in the event of hardware or software failure.
Registry           The Windows NT/2000 configuration settings database.
                   This database stores configuration data about the hardware and the
                    system environment of the computer. This consists of the contents of
                   the SYSTEM.DAT and USER.DAT files.
Replica            A host computer containing a copy of the Master data, created by the
                   replication process.
Replication Tree A unique definition of the replication procedure that maps replication
                 flow between one Master and any number of Replica nodes.
Replication         The process of transferring changes that occurred on the Master, to the
Synchronization     The process that reconciles any data differences between servers at a
                    certain point in time.

Page 2                XOsoft White Paper – IT Challenges in the Business Continuity Market
IT Challenges in the Business Continuity Market
         There are many replication tools available on the market today, but not all of them
         have the same capabilities. When IT professionals approach the task of
         implementing an online replication solution over WAN that will provide them with
         100% business continuity and peak performance, they encounter numerous
         technical challenges.

Heterogeneous        Maintaining high levels of access to information across heterogeneous
Systems              systems without compromising a quality user experience is a challenge
                     for any IT organization.
                     The complexity of today’s distributed applications – the large number
                     of applications, servers, operating systems, databases and network
                     components, – makes it more difficult to achieve high availability and
                     automatic disaster recovery.
                     To understand the complexity of today’s technology environment,
                     let’s look at a typical corporate data center.

                                             Figure 1: Heterogeneous System

                      Data centers typically consist of multiple tiers of systems that include
                      Web servers, application servers and backend corporate database
                      servers. Web servers (Internet/Intranet) handle incoming requests,
                      routing them to the appropriate application server. Application servers
                      implement the logic required to service requests. They execute the
                      business logic and periodically query or update the corporate database
                      as required by the business logic.

Page 3                  XOsoft White Paper – IT Challenges in the Business Continuity Market
Keeping data        An online replication mechanism should enable immediate
up-to-date and      accessibility to a live Replica, or up-to-the-moment backup of the
consistent at all   critical data, in the event of a fatal system or software failure.
times               Capturing changes and replicating them securely and in real-time over
                    WAN links (while overcoming connectivity disruptions), is not a
                    trivial matter.
                    Along with the rise in availability requirements, the need for data
                    integrity also continues to be a high priority. A transaction must be
                    executed perfectly and acknowledged — or it will not qualify as a
                    transaction. There is no middle ground.
                    There are many ways in which data may be corrupted – an incorrect
                    replication process, connectivity problems during synchronization,
                    viruses. Protecting data against these potential culprits and having
                    recovery processes in place will ensure data integrity.
                    Given the obstacles that exist today, few, if any, multinational firms,
                    for example, are capable of real-time recovery of global applications.
                    Instead, they simply recover applications at local sites and reconcile
                    changes around the world.

Performance         Downtime is not the only concern when considering high availability,
                    – for many organizations, stringent processing needs force IT leaders
                    to ensure high performance. This is especially true with applications
                    that provide services directly to end users and consumers. One
                    problem with many data synchronization solutions, is that they may
                    unduly reduce the performance and network throughput of the
                    computer that is the source of the data.
                    The requirement to replicate data to multiple, geographically removed
                    sites, only worsens this problem, especially affecting network
                    throughput. This may cause response time to users to fluctuate,
                    decreasing the reliability and availability of the application.

Keeping costs       Though business continuity solutions are implemented primarily to
low                 prevent considerable revenue loss, many companies are still sensitive
                    to the cost of such a solution.
                    One of the problems facing IT management, is that most typical
                    corporate networks are made up of a mesh of computer equipment
                    purchased from several different vendors, running on a variety of
                    operating systems.
                    Most replication solutions on a non-standardized network may be very
                    costly, or require complex (and error-prone) manipulations.
                    Attempting to standardize the networked system may in itself be
                    costly, and may require the purchasing of new application versions or,

Page 4                XOsoft White Paper – IT Challenges in the Business Continuity Market
                  worse yet, may require rewriting existing applications, to allow them
                  to work with the new standard platform. Given the constant dynamics
                  of change in software and hardware requirements, the system may
                  again revert to being non-standard, within a relatively short period of
                  Therefore, an optimum replication solution must be highly flexible,
                  yet robust enough to be able to handle any foreseeable combination of
                  standard and non-standard system network components.

                  Bandwidth requirement imposed by a replication solution are an
                  additional critical factor greatly affecting cost. While fiber optic
                  connections may be used to reliably and securely distribute data over
                  great distances, it is obvious that this type of infrastructure carries a
                  very high price tag. For an international company that must maintain
                  synchronized data centers around the world, it is important to have a
                  replication solution that does not congest the pipes and works
                  efficiently over high-latency, low-speed networks, and eventually
                  helps to minimize connectivity costs.

WAN challenges Keeping data centers synchronized over a Wide Area Network,
               whether private or public, poses numerous challenges.
               Wide Area Network communication is by nature less reliable than
               Local Area Network communication, and is more prone to
               disconnections and performance drops. WAN links traverse great
               distances and many switching points, and are therefore susceptible to
               a relatively large number of potential points of failure.
               Another concern, when using public networks and the Internet in
               particular, is security. Business critical information is passed over
               WAN links when synchronizing data, and it is imperative to ensure
               secure data transfer.

Disruptions       When discussing a business continuity solution, it is obviously
                  important that the solution itself does not cause any disturbance in the
                  business processes.

                  Possible disruption starts with the installation process. Due to the
                  complexity of the systems, most replication solutions require the
                  machine to reboot, to complete installation, or prohibit activation
                  while applications (databases in particular) are up and running.
                  Another potential problem is that system users may suffer reduced
                  system performance during the replication process.

Page 5              XOsoft White Paper – IT Challenges in the Business Continuity Market
Overcoming the Hurdles with WANSync
         XOsoft, a leading provider of high availability and disaster recovery software
         solutions, has developed WANSync, as the definitive, WAN-based business
         continuity platform.
         In this section, we will show how WANSync addresses the various requirements of
         an effective disaster recovery and/or high availability solution, and how it
         overcomes all the challenges described in the previous section.

Non-                 It is extremely important that any online replication solution not
intrusiveness        interfere with business continuity at any stage. XOsoft has
                     implemented several mechanisms to ensure that the installation and
                     operation of the WANSync solution does not interrupt service
                     provided to the end users:
 Soft Installation Installation of WANSync, whether on Windows or UNIX servers, does
                   not require a system reboot or application shutdown. The WANSync
                   replication agent is installed as a daemon on UNIX and as a Windows
                   service on Windows NT/2000 systems.
 Soft Activation     WANSync is engineered to “jump” onto open files and start
                     synchronizing servers as soon as the first connection with the remote
                     server has been established. This feature enables replication of files
                     that are always kept open, to start replicating without shutting down
                     the application.
 Non-intrusive       WANSync enables files to be updated at the same time that they are
 update              being opened by users, without resulting in error messages or server
                     performance degradation.
                     Processes that open a file in shared mode (default on UNIX) before
                     replicated updates arrive, will still see the unchanged version of the
                     file, while all new processes will be referred to the updated version.
                     If a file is opened in exclusive mode (default on Windows systems)
                     WANSync will wait until the file is closed, or the predefined timeout
                     expires, and will overwrite the file as soon as the lock is released.

Tree-structure       Modern enterprise networks, with geographically distributed
Communication        computing resources, present a complicated topology. Multiple
                     replicated servers connected to the same source of data may
                     significantly affect Master server performance. This configuration
                     imposes strong bandwidth constraints and does not scale well. At the
                     same time, one cannot assume that there is a direct connection
                     between the Master and all Replica hosts. The tree topology structure
                     (Figure 2) adopted by WANSync, provides a fast and scalable solution
                     for distributing data to multiple locations, reduces load on the Master
                     server and brings significant savings in network bandwidth.

Page 6                 XOsoft White Paper – IT Challenges in the Business Continuity Market
                  Each host in a replication tree needs a TCP connection only with its
                  direct descendents. However, each member of the tree is fully aware
                  of the topology of the entire tree, and its own position in the structure.

                                         Figure 2: Tree and Star Topologies

 Proprietary   To support this topology, XOsoft has developed a proprietary inter-
 Communication process communications protocol – application-layer software based
 Protocol      on the TCP transport-layer protocol, optimized to support low speed,
               highly intermittent TCP/IP connections.
               Besides the routing and addressing mechanisms required to support a
               tree topology, the WANSync communications protocol provides an
               acknowledgement mechanism at the transport level, to overcome loss
               of packets and ensure that packets do not arrive at the target in a
               different order than the one in which they were transmitted.
               In addition, the protocol provides support for data compression,
               security and encryption (WANSync incorporates secure SSL
               The following illustration (figure 3) shows a tree, where data
               replication flows from the master host (NY) directly to three Replica
               nodes (Tokyo and London), and continues from London to Frankfurt.

                              Figure 3: WANSync Replication Tree

Page 7              XOsoft White Paper – IT Challenges in the Business Continuity Market
                    WANSync may be operated in a number of configurations, including:
 Single Master      A One-to-many mode, where a single Master is synchronized with
 Replication        multiple Replicas.

 Collective         A Many-to-one mode, where information from multiple servers is
 Replication        collected and consolidated in a single, replicated server.

 Multi-Master       A Many-to-many mode, where two or more hosts are synchronized
 Replication        with each other. The simultaneous replication of the same file from
                    several Masters is forbidden.

               One-to-many                Many-to-one                  Many-to-many

Multiple trees      To enable selective replication of data to different destinations,
                    WANSync supports multiple replication trees (i.e. each host may
                    function as a Master in one tree and as a Replica in another tree).
                    This feature does not require installation of additional WANSync
                    instances on the host – one daemon/service may serve multiple trees.

                                       Figure 4: Multiple Replication Trees

Page 8                 XOsoft White Paper – IT Challenges in the Business Continuity Market
Replication       The WANSync replication mechanism maintains Replicas of databases
 Real-time        and/or file systems by continuously capturing changes and
 Capture of       immediately transmitting them to Replica sites.
 Changes and      WANSync replication technology captures changes to any file managed
 Incremental      by the server operating system at the byte level, and without
 Updates          interfering with the write process. This is accomplished by installing a
                  file-system filter driver, which filters all transactions sent to the file
                  system, and is transparent to applications. Therefore, WANSync is
                  aware of any change made in real-time, without performing disk scans
                  or file comparison procedures. By enabling the detection of byte-level
                  changes, this technology minimizes replicated data to the absolute
                  minimum, and performs incremental updates only on replicated
                  This feature minimizes performance impact by keeping Replica
                  servers updated at any moment in time.
 Journaling and   WANSync supports replication of data in both journaling and
 Aggregation      aggregation modes to provide a comprehensive solution for all types
                  of servers (file, application or database servers).
                  Journaling mode is needed for synchronization of servers that require
                  transactional data integrity (for example, database servers or
                  Exchange server). Journaling enables replication of files that are
                  always kept open by their application, by recording all operations
                  performed on open files in a journal log file. The journal is transferred
                  to Replica sites in real-time or according to the customer-defined
                  schedule, and the operations recorded in the journal are replayed on
                  the replicated files. This ensures that all write operations are
                  performed on the Replicas exactly in the same order they were carried
                  out on the Master machine. Therefore, data integrity is preserved at all
                  If aggregation mode is used, WANSync not only queues and transfers
                  incremental updates, but also aggregates changes accumulated in the
                  replication queue in real-time. Applying this mode guarantees that the
                  smallest amount of changed data is transferred over the network. In
                  aggregation mode, changes are replicated as soon as files are closed
                  by their application.
                  Journaling and aggregation modes are mutually exclusive and cannot
                  be used simultaneously in the same replication tree.

Page 9              XOsoft White Paper – IT Challenges in the Business Continuity Market
                          Figure 5: Journaling vs. Aggregation

Flexible      While changes are always captured in real-time, WANSync provides
Replication   flexible scheduling policies to define when updates should be
Scheduling    transmitted and applied to Replica servers. Although the highest level
              of data protection is provided by immediate replication of changes,
              you may also schedule transfer of data at fixed time intervals, or at
              certain times of the day. The replication schedule is set for each
              Master host. In addition, any Replica host may be configured to delay
              the transmission of replication data down the tree to its descendants.

                            Figure 6: Replication Scheduling

Page 10         XOsoft White Paper – IT Challenges in the Business Continuity Market
Flexible          For both real-time and scheduled replication, WANSync allows
Bandwidth         bandwidth consumption to be regulated, consequently avoiding
Consumption       network congestion and ensuring equitable bandwidth access to other

Synchronization   Synchronization must be carried out before the replication process
                  starts, to ensure that all hosts have an identical copy of data. It should
                  also be performed after any critical failure or network disconnection,
                  or when a maintenance operation has caused the replication process to
                  stop for a long time. The same process is used, but in the opposite
                  direction, during recovery of Master data from a Replica.
                  Synchronizing large sets of data between master and replica servers
                  may be a time consuming process. WANSync addresses the following
                  major synchronization challenges:
 Minimal          WANSync works with minimal bandwidth requirements by sending
 Bandwidth        only differences in files, not only during the replication process, but
                  also during file synchronization. The proprietary binary-diff
                  synchronization algorithm employed by the WANSync solution allows
                  two files to be compared without requiring them to be present at the
                  same site, and transfers only differences across the network. WANSync
                  utilizes this mode for efficient synchronization of large data files and
                  databases. This feature saves significant bandwidth, and provides a
                  fast, robust, – and in many cases, the only solution for synchronization
                  of large data sets.
 Simultaneous    WANSync does not stop tracking new changes while the
 Replication and synchronization process is running. All new changes are stored in the
 Synchronization replication queue and are applied to Replicas as soon as
                 synchronization is complete. This allows up-to-date copies of data to
                 be created without suspending update activity on the Master server.

Page 11             XOsoft White Paper – IT Challenges in the Business Continuity Market
                      Figure 7: Simultaneous Replication and Synchronization

                   WANSync can automatically initiate synchronization without manual
                   intervention, when a data inconsistency is discovered between Master
                   and Replica hosts. This is usually a result of a long interruption in the
                   replication process that can cause an overflow of the replication queue
                   when new updates are stored but not transferred to a Replica host.

Protection from If the data on the Master server is corrupted, the corrupted blocks may
Data Corruption propagate to Replicas as well. WANSync protects business critical data
                against this scenario, as follows:
 Rollback          WANSync can save a history of changes (snapshots) on a Replica host
                   for a set period, and provides the ability to roll back these changes
                   upon user request. This feature not only protects Replicas against
                   propagation of corrupted data from the Master, but also allows Master
                   data to be recovered from the protected Replica.

Page 12              XOsoft White Paper – IT Challenges in the Business Continuity Market
                                            Figure 8: Data Rollback
 Delayed Update Another approach to protection against data corruption is to delay
                changes to one or all Replicas. The proposed configuration is to have
                one up-to-date Replica with real-time replication with another Replica
                remaining a number of minutes or hours behind (as illustrated in
                Figure 9). This ensures that the latest changes are not lost if
                production servers crash, and at the same time, enhances protection
                from data corruption as the replication process may be halted before
                corrupted blocks are propagated to secondary Replicas.

                                  Figure 9: Delayed Replication

Replication of    Applications running on Windows platforms often make changes to
System Settings   system settings (referred to as registry keys). Replication of system

Page 13              XOsoft White Paper – IT Challenges in the Business Continuity Market
                 settings is required to provide a comprehensive solution for
                 application standby servers.
                 Replication of registry keys is optional and must be enabled by the
                 user. The selection of registry keys to be replicated is facilitated by the
                 WANSync user interface, which enables browsing the registry on each

Integrated       For major relational databases, an integrated client interface provides
Database         easy-to-use replication setup by mapping database components
Interface        (tablespaces, log, archive, control and other associated files as
                 illustrated in Figure 10).

                    Figure 10: Automatic Mapping of Database Components

Cross-platform   WANSync supports synchronization and replication of data between
Replication      servers running different operating systems. WANSync transfers data
                 in a binary mode, and preserves file and directory attributes, including
                 ownership, creation and modification time and read-write-execute
                 permissions. While some UNIX attributes are meaningless on
                 Windows NT/2000 systems, once data is recovered, its original state
                 is restored.

Page 14            XOsoft White Paper – IT Challenges in the Business Continuity Market
                                    Figure 11: Cross-platform Replication
                 The ability to replicate data across platforms (for example from
                 expensive UNIX servers to relatively inexpensive Windows
                 machines) provides a very cost-effective solution, for both disaster
                 recovery and remote backup.

Centralized      WANSync Manager is a windows-based application that provides
Management       administrators with centralized management and monitoring of all
and Monitoring   participating hosts from any single, remote site. It takes just minutes to
                 install and configure, and features an extremely easy-to-use graphical
                 user interface.
                 WANSync Manager allows system administrators to receive
                 notification of selected events via email, or by executing a user-
                 defined script.

Page 15            XOsoft White Paper – IT Challenges in the Business Continuity Market
      The following table summarizes the technologies and mechanisms implemented by
      the WANSync solution to answer the challenges of an optimal business continuity

          Challenge                                 WANSync Solution
          Heterogeneous systems                     Journaling and Aggregation
                                                    Cross-platform Replication
          Keeping data updated and consistent at    Replication
          all times                                 Synchronization
                                                    Journaling and Aggregation
                                                    Protection from Data Corruption
                                                    Replication of System Settings
          Performance                               Real-Time Capture of Changes
                                                    Tree-structure communications
          Keeping costs low                         Incremental Update
                                                    Minimal bandwidth synchronization
                                                    Tree-Structure Communication
                                                    Cross-platform Replication
          Disruptions                               Non-intrusiveness
                                                    Simultaneous Replication and
          WAN Challenges                            Communication Protocol

Page 16                 XOsoft White Paper – IT Challenges in the Business Continuity Market
WANSync Products
       WANSync comprises a comprehensive suite of real-time replication and
       synchronization solutions, including:
       •   WANSync Server - for increased protection for application servers of any type,
           including open files and system settings.
       •   WANSync Exchange - the definitive WAN-based integrity and availability
           platform for Microsoft Exchange.
       •   WANSync SQL - the most comprehensive WAN-based disaster recovery platform
           for SQL databases.
       •   WANSync Oracle - the unrivaled WAN-based disaster recovery platform for
           Oracle databases.

A 14 day trial evaluation of the software is available for download at:

       WANSync provides true cross-platform, carrier-grade business continuity over a
       variety of synchronized server topological configurations, with minimal bandwidth
       requirements. Regardless of the type and severity of the challenges your
       information infrastructure may face, WANSync allows you to…

                                                                          Just Keep Working.

Page 17                XOsoft White Paper – IT Challenges in the Business Continuity Market

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