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====Introduction====
Today many businesses struggle to balance the need for systems that can support mission-critical applications and pressures to reduce total cost of ownership for IT infrastructure. SteelEye enables businesses to get the best of both worlds - high availability on Linux.

Linux provides a high performance, reliable, open-source solution and its low cost makes it the platform of choice for companies that are targeting the new Web economy. SteelEye enhances the stability and power of Linux with LifeKeeper - a commercially proven, high availability software solution that provides fault-resilience to support mission-critical applications.

====High Availability on Linux====
SteelEye's LifeKeeper for Linux is a software application that ensures the continuous availability of applications by maintaining system uptime. LifeKeeper maintains the high availability of clustered Linux systems by monitoring system and application health, maintaining client connectivity and providing uninterrupted data access regardless of where clients reside - on the corporate Internet, intranet or extranet.

To enable automatic system and application recovery if the system goes down, LifeKeeper allows applications to failover to other servers in the cluster. This helps LifeKeeper minimize the risk of a single point of failure and allows Linux systems to meet the stringent availability requirements of mission-critical operations by creating a fault resilient environment.

====Fault Resilience====
LifeKeeper provides fault resilience for Linux environments by enabling other servers in a cluster to take over for failed servers or failed applications. Total cost of ownership is reduced, because LifeKeeper supports an active-active server configuration. This model eliminates the need for extra servers dedicated for hot backup and allows clients and applications to failover to other production servers in the cluster.

====Proactive Protection====
With LifeKeeper, hardware component or application faults are detected in advance of a full system failure through multiple fault-detection mechanisms. LifeKeeper monitors Linux clusters using intelligent processes and multiple LAN heartbeats. By sending redundant signals between server nodes to determine system and application health, LifeKeeper confirms a system's status before taking action. This reduces the risk of a single point of failure and minimizes false failovers. LifeKeeper also limits unnecessary failovers by recovering failed applications, without a full failover to another server, if the hardware is still active.

[[Image:steeleye\_heartbeat.jpg]]

====Transparent Failover====
If an event creates an interruption in a server's availability, LifeKeeper automatically moves the protected resources and applications to another server in the cluster. Because this switchover is transparent to clients, a system failure does not impact users' productivity. LifeKeeper migrates all applications and transfers connectivity in such a way that clients have continuous access to applications and data. This ensures that all clients - from internal users to customers shopping online - are not affected by unanticipated system failures.

====Scalability====
LifeKeeper provides a cluster framework to allow the number of users supported by an application to be increased by simply adding nodes into the cluster. To ensure protection from failures, LifeKeeper also supports scalability at the application level. When LifeKeeper is installed with a multi-directional configuration, applications that are running on one machine can be broken up and failed over to separate machines.

[[Image:steeleye\_scale.jpg]]

====Data Access and Integrity====
In the LifeKeeper shared-storage environment, data storage is separate from the servers in the cluster. All data is stored on a shared disk array. This independence allows data to be accessed regardless of which server is being used to host the application. Additionally, LifeKeeper's shared storage locking mechanism helps maintain data integrity by locking the drive so that only one application can access specified data at one time.

====Recovery Operations====
LifeKeeper provides protection for Linux environments to support disaster tolerance, multiple system failures or faster recovery, including:

• Multi-directional Recovery<br>LifeKeeper for Linux supports a four-node cluster in a multi-directional failover configuration within the context of two nodes connected to the same shared disk.
  [[Image:steeleye\_multi\_dir.jpg]]
• Shared Data Support<br>LifeKeeper for Linux provides for an N+1 configuration. LifeKeeper supports up to two nodes per shared SCSI bus. This allows shared SCSI disk-based application recovery between two nodes within the cluster that are connected to the same shared disk. In this configuration, one server, in an active-active role, provides backup for failovers from any of the other nodes in the cluster.
  [[Image:steeleye\_shared\_data.jpg]]
• Cascading Failover<br>LifeKeeper for Linux allows cascading failover for as many as 32 active nodes to ensure continuous client access in the event of system or application failure.
  [[Image:steeleye\_cascade.jpg]]

====Application Recovery Kits====
SteelEye offers LifeKeeper Application Recovery Kits for packaged software, including databases, Web servers and application servers. These Application Recovery Kits include tools and utilities that allow LifeKeeper to manage and control a specific application. When an Application Recovery Kit is installed for a specific application, LifeKeeper is able to monitor the health of the application and automatically recover the application if it fails.

SteelEye also provides an Application Recovery Software Developer's Kit (SDK) that supports the development of custom Application Recovery Kits. The Application Recovery SDK offers a powerful framework for developing customized recovery routines for proprietary applications as well as commercial application servers. Using SteelEye's Application Recovery SDK, special recovery routines can be defined by assembling straightforward application recovery scripts.

====Uptime During Maintenance and Upgrades====
LifeKeeper enables continuous operations during planned downtime for maintenance or upgrades as well as in the event of a system failure or if an application ceases to respond. The fault-resilient capabilities of LifeKeeper can be leveraged to facilitate system or application upgrades. With LifeKeeper, the amount of downtime required for common maintenance tasks and upgrades is significantly reduced or eliminated.

===System Requirements===

LifeKeeper for Linux Configurations and Optional LifeKeeper Data Replication for Linux

'''System Requirements:'''

• Following distributions of the Linux Operating System:
  • Red Hat Enterprise Linux 3.0 and 4.0
  • Red Hat Advanced Server 2.1
  • SuSE SLES 8 and SLES 9
  • Asianux 1.0
  • White Box Enterprise Linux 3.0
• Following scripting environments:
  • perl 5.00503 (or later)
  • Korn Shell pdksh 5.2.14 (or later)
• TCP/IP-based network communication
• Minimum memory requirement: 64 MB

'''Server Requirements:'''

• Any Intel-based IA32/IA64/AMD64/EM64T servers
• IBM POWER5 servers including pSeries/Linux and OpenPower

'''Shared Storage Options:'''

• Any Network Attached Storage device
• Fibre Channel-based adapters similar to those from Emulex or Qlogic
• SCSI-based adapters similar to those from Adaptec
• Support for SCSI-2 Reservations, Inquiry, and Test Unit Ready commands
• Controller with 2 I/O Ports (SCSI External Disk Array)
• Linux SCSI support via the standard SCSI driver through both /dev/sd and /dev/sg servers

Disk Space Requirements:

The LifeKeeper core package requires the following disk space:

• /opt approximately 10 MB of storage
• / approximately 25 KB of storage

Complete Configuration Support Matrix:

http://www.steeleye.com/pdf/literature/ConfigMatrix.pdf