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HP Serviceguard Solutions for Linux

Guest blog written by Ravichandra Krishnamurthy, HP Serviceguard Technical Architect

 

The HP Serviceguard for Linux (SG/LX) solution ensures high availability of enterprise workloads. It monitors many aspects of cluster health including health of network paths, storage connectivity, volume monitoring, and data replication status.

 

SG/LX is a cluster implemented at the user-level which shares most of its implementation with Serviceguard for HP-UX. Serviceguard for HP-UX has been in the market for over 20 years and is well known as the best in the industry for its availability, robustness and prevention measures against data corruption.

 

SG/LX comes with many existing and new features, of which some of the newer ones are described here.

Availability

  • Live Application Detach (LAD): enables administrators to perform HB network maintenance or maintenance on one or more nodes of the cluster or the entire cluster when the workloads are online.
  • Maintenance can be easily performed by two of the maintenance modes
    1. Partial startup maintenance mode helps in performing maintenance on a single resource while the workload is partially started by bringing up some resources so as to allow easy maintenance on one of the other resources.
    2. Placing a running workload into maintenance mode so that network or a few other resources can be examined and maintenance performed on them without the workload having to failover to another node
  • Online workload reconfiguration: helps administrators add, modify or delete resources from a running workload without having to bring them down at all
  • Rolling Upgrade: helps users to migrate from one version of SG/LX to the next, as well as upgrade the current version with a patch, in a rolling fashion, while keeping all the workloads running on other nodes of the cluster.

Robustness

  • Various server and disk based Quorum methods are available as arbitration mechanisms, to handle network partitions, when they occur. These arbitrators uniquely elect one of the partitions and ensure that all workloads in the cluster are moved to this partition after ensuring I/O quiescence from the other partition is complete.
  • Deadman kernel driver (a mechanism used by SG/LX) ensures that a node which loses its membership in a cluster, due to network partition or any other reason, is rebooted within a certain duration.

Prevention measures against data corruption

  • SCSI-3 Persistent Reservation is used by SG/LX to ensure that only the node that is running the workload is allowed to perform write I/Os to its shared storage disks. As part of cluster reconfiguration, SG/LX includes I/O quiescence stage. This stage comes right after the stage where deadman driver has ensured that nodes who lost membership, have been rebooted and allows time for disk I/O from evicted nodes to complete.

 Handling workload dependencies

  • SG/LX provides multiple ways to specify the dependencies between workloads, providing a rich set of dependency description directives that helps administrators to easily configure and handle dependencies between workloads.

Health and connectivity monitoring

  • SG/LX comes with a wide array of monitoring capabilities, which includes network layer 2 and layer 3 monitoring, storage connectivity monitoring as well as host-based data replication status monitoring, and the capability to affect failover based on this.

 

SG/LX supports many mechanisms for building in redundancies in its configuration, including that of multiple paths for Heartbeat and data network using Linux network bonding, and multiple paths to storage using multipath. In its disaster recovery products like, Extended Distance cluster, Metrocluster and Continentalclusters, it uses multiple switches, routers and FC switches, configured and connected in redundant ways to build in redundancy in the various paths between the sites.

 

It also supports Linux distributions like RHEL and SLES on x86 platforms. Virtualization technologies like VMWare and KVM are supported, allowing administrators a choice of combinations of physical servers and virtual guests in a cluster. This helps to reduce IT costs by using virtual guests for standby nodes or recovery sites, in case of active-standby configurations. SG/LX supports customized toolkits for providing HA for well-known applications like SAP, SAP Sybase ASE and Sybase Replication Server, Oracle, NFS, and Enterprise DB PPAS. Well known configurations of these applications are supported as part of these customized HA toolkits.

 

HP Serviceguard for Linux provides a comprehensive set of solutions ensuring high availability and disaster recovery for the mission critical needs of enterprise workloads. I will write more about of the unique capabilities of this solution in the coming weeks.

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