Parallels H-Sphere Documentation System Administrator Guide

 

Understanding Load Balancing in H-Sphere

(H-Sphere 3.0 RC 1 +)
 
 

Related Docs:   Installation of Load Balanced Web/Mail Clusters in H-Sphere Implementation of Load Balanced Cluster in H-Sphere Load Balanced Server Clusters (Admin Guide)

Last modified: 27 Dec 2007

 

WARNING: This documentation covers Parallels H-Sphere versions up to 3.1. For the latest up-to-date Parallels H-Sphere documentation, please proceed to the official Parallels site.

Figure 1: Simple Load Balanced system with one web cluster.

It is possible to add load balanced (LB) Web and mail clusters to H-Sphere. Load balancing implies balancing server traffic amongst multiple computers (LB cluster) which H-Sphere regards and operates with as a single server.

Load balanced cluster solution in H-Sphere requires 4 or more physical servers:

  • Load Balancer: any solution like Cytrix® NetScaler for balancing traffic across the web/mail servers. Load Balancer directs traffic to another server if the first one is currently overloaded. It can also allow the service to continue even if one of the servers is down.
  • One master and one or more slave servers form a load balanced Web/mail cluster. All these servers are being added to H-Sphere as physical servers, with all related packages installed, but H-Sphere logical servers are created only on master servers, and H-Sphere operates with load balanced cluster only via master server.
  • NAS (Network Attached Storage): shared storage for master and slave servers. NAS is a highly reliable server with enough space for storing data. Web/mail content directories are mounted to the NAS where the content is actually stored. Web and mail servers can jointly use one NAS or have their own NAS for Web and for mail.

 

Load Balancers

You need to purchase, install and configure any load balancer solution, for example, Cytrix® NetScaler.
This task is beyond the scope of H-Sphere documentation.

Figure 2: More complex Load Balanced system with two mail and two web clusters

 

Supported NAS

The following file storage systems are supported by H-Sphere:

NAS Notation Supported in H-Sphere
Generic Linux NFS UNIX 3.0 RC 1 and up
RedHat GFS UNIX 3.0 RC 4 and up
NetApp NET_APP 2.3 and up to 2.5
3.0 RC 1 and up
BlueArc BLUE_ARC 2.4.3 Patch 10 and up
2.5 Beta 5 and up
EMC Celerra EMC_CELERRA 2.4.3 Patch 10 and up
2.5 Beta 5 and up

Note: In H-Sphere 3.0 Final and up all H-Sphere customers will be recommended to choose shared Linux NFS as the most simple and reliable solution supported by PSoft.


 

Load Balanced Cluster

Loab balanced cluster consists of one master and one or more slave servers regarded by H-Sphere as a single server.

  • Master and slave servers are added to H-Sphere as physical servers.
  • Master-slave relations between these servers are set in admin CP.
  • Only master server is added as Web/mail logical server to H-Sphere. CP communicates only with master server.
  • Requests are passed to external IPs routed by the load balancer. Load balancer distributes requests evenly across the master and slave servers (internal IPs corresponding to external IP). For this purpose, NAT must be properly configured on load balanced cluster servers.
  • Master and slave server share the same H-Sphere related directories where all user content, scripts, and the majority of H-Sphere related binaries are located. These directories are actually stored on the NAS and mounted from master and slave servers via NFS.
  • Along with shared storage, master and slave servers have their own unique IP-specific logs and configs which are synchronized by special cron scripts run on these servers.

See load balanced cluster scheme with generic Linux NFS shared storage.


Related Docs:   Installation of Load Balanced Web/Mail Clusters in H-Sphere Implementation of Load Balanced Cluster in H-Sphere Load Balanced Server Clusters (Admin Guide)



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