Study on Management Agent Failover and Refresh Mechanism

1. Study on Management Agent Failover and Refresh Mechanism Esquivel C. Malillos CS526

2. Introduction • Currently implemented by Hewlett Packard’s HSV Element Manager software application. • Manage and monitor a proprietary controller array called Enterprise Virtual Array (EVA) • Written as Java applet. • Agent Failover • Refresh Mechanism

3. Storage Area Network • High speed special-purpose network. • Use fiber channel technology. • Supports disk mirroring, backup and restore, data migration from one storage device to another. • Replication • Sharing of data among different servers in the network From www.emulex.com

4. Web-Based Enterprise Management • Unifying mechanism for describing and sharing management information. • Common UI framework. • Problem addressed: Multiple platforms have no easy way to obtain management data from different operating system - proprietary API or console for each application.

5. Management Agent • Application running in a management server that manages and monitors storage array. • Serves as an intermediary server between the storage array and web browser client (WBEM). • Storage Array could be managed by multiple agents either in active-active or active-passive mode. • Storage Array could be accessed through multiple web browser clients. • Multiple agents maintain a same view of the SAN and EVA by accessing a common Management Logical Disk (MLD) that serves as the controller’s database through firmware’s API.

6. Management Agent Web Screen Shot

7. Failover and Refresh Applet • Java applet that runs in the background of the web browser. • Send keep-alive message to the agent in a regular interval. • Two information is available from the server’s reply to the poll: agent list and status information. • Automatically or manually redirects the browser to another agent. • Use status information for browser refresh mechanism.

8. Applet Parameters • Run – enables/disables loading and initialization of the applet. • Auto – enables/disables agent failover without user interaction. • States – list of status fields the applet is to monitor for changes. • Poll - enables/disables polling of the server. • Interval – time interval between applet polls. • Retry – number of attempts to connect with the server before declaring an agent failure.

9. Agent Failover Mechanism When it happens? • If the management agent did not respond to a keep-alive message sent by the applet after a fixed count of retries. How? • Manually – the applet pop-up a box with a URL list of available agents that the user could choose. • Automatic – the applet automatically redirects the user to a known agent by looking sequentially to the internally managed agent list. If the first agent in the list is passive or unreachable, it tries the next one and so forth … until it founds one that works.

10. Browser Refresh Mechanism When it happens? • The agent response contains a string composed of numbers separated by commas. Each number corresponds to an object of the EVA controller. If the string is different from the old string stored by the applet, a refresh is invoked. How? • The applet store information about the last received state string text. It compares the new with the old one. If different and the number corresponds to the state parameter of the applet, the applet calls Java appletContext::showDocument() to reload the page.

11. Conclusion • Currently operational and shipped to customers. • Areas of improvement • Use apache as HTTP server rather than proprietary HTTP server called ELM. • Dynamically put the applet in browser pages rather than statically through Java servlet. • Filter non-operational management agent. • On-the-fly modification of applet parameters.

12. References • http://www.winnetmag.com/Articles/Index.cfm?ArticleID=3568. • Vacca, J.R. The Essential Guide to Storage Area Networks. Prentice-Hall, Inc. 2002. • Lord, R. Bridge Failover and Page Refresh Mechanism. Sept.9, 1999.