Transcript Study on Management Agent Failover and Refresh Mechanism

Study on Management Agent
Failover and Refresh
Mechanism
Esquivel C. Malillos
CS526
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

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
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.
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.
Management Agent Web Screen
Shot
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.
Client Machine
Browser
General-purpose network
Failover path
Primary path
Bridge Agent Host
A
Fibre channel network
Management agent
Bridge Agent Host
B
Management agent
Storage System
HSV100
Controller
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.
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.
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.
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.

References
http://www.winnetmag.com/Articles/Index.c
fm?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.
