Remote Management: TCSWAT supports cluster management and monitoring from any Web browser.
* Easy installation and configuration
* EnlightenDSM management tool
* Strictly IP-redirection application support
* Lacks automated configuration for simple clusters
TurboLinux’s TurboCluster Server 4.0 supports clusters that exceed 25 servers and provides an affordable and scalable Internet-server solution. It’s a one-box solution that includes both management tools and a copy of Enlighten Software Solutions, Inc.’s EnlightenDSM cross-platform cluster-management suite.
TurboCluster is not a generalized clustering system. Instead it restricts itself to IP forwarding, which works well for Web-based servers such as the Apache Web server, SMTP, POP and IMAP mail servers, FTP servers, and news servers.
TurboCluster uses a fast, kernel-based Advanced Traffic Manager (ATM) that reroutes IP traffic to the appropriate computer in the cluster. Load balancing consists of distributing these requests among servers within a cluster. The servers respond directly to the sender when the forwarded request is received, which helps minimize network traffic.
TurboCluster does not provide clustered application support, whereby programs running on several servers are managed by a transaction monitor that provides advanced features like transaction-level failovers and rollbacks. That type of support is needed for Linux to attract the more sophisticated Web applications that are now being developed for other platforms.
Advanced Traffic Manager runs on a TurboCluster server, and there can be multiple ATM servers with additional servers being hot spares. These can automatically step in should the primary server fail. The servers that the ATM controls can be any server from Linux to Solaris, to Windows NT. This is possible because the Advanced Traffic Manager simply forwards requests and remotely monitors server activity. When a server in the cluster no longer responds to polling, it will receive no more requests, effectively removing the server from the cluster.
TurboCluster supports two types of connections between the Advanced Traffic Manager and servers. The most common is direct IP connections, while the other uses IP tunneling that provides an encrypted link and is handy when cluster servers are at different locations. In fact, TurboCluster can spread cluster servers throughout the Internet or an insecure intranet. The connection type is server-specific, so there could be many local servers and a few remote servers in a single cluster.
Installing and managing a TurboCluster was remarkably easy with direct IP connections. We set up two servers with Apache and FTP servers that shared access to an NFS server so that common Web and FTP directories could be used by both systems without needing special replication support. A pair of TurboCluster servers was set up as a primary and backup Advanced Traffic Manager.
Configure it Out: TurboCluster’s turbonetcfg is extended to handle both cluster and NFS cluster configuration.
We started out with the console-based management tool, turbonetcfg, which adds cluster extensions to the normal network-configuration support. It was simple to set up a cluster, add the two servers, and then include the Web and FTP services to the servers’ list of capabilities. We also had to configure minor items like the administrator’s e-mail address, but the installation time wasn’t much more than a typical server setup. We then used the turbocluster_sync program to broadcast the configuration.
When we disconnected a cluster server and later the primary Advanced Traffic Manager, the overall system kept running with only an occasional loss of the request that was being processed when the server was disconnected. Clicking the “Refresh” button on the client’s Web browser usually restored things to normal.
We eventually switched to using the Web-based management tool, TCSWAT, and then EnlightenDSM. We were impressed with EnlightenDSM’s ability to monitor a variety of platforms, including Linux and all varieties of Microsoft Windows. While it requires some additional configuration, it can address PCs that aren’t part of a TurboCluster, including workstations.
TurboCluster is a great place to start given Linux’s acceptance in the Web area. The inclusion of EnlightenDSM allows managed distribution of the cluster servers across the Internet if necessary, making TurboCluster an excellent choice as long as the applications you are using are suitable. While there will be improvements, it is not clear how upgrades will address other clustering technologies such as middleware and backend management. Transaction systems, distributed object brokers, and related distributed management systems will be needed before Linux can take on all of the chores currently addressed by high end systems like those from Sun.
TurboCluster is only the beginning when it comes to cluster technology. It’s definitely a solid pick for anyone needing more power or higher reliability from a single Linux PC server.
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