Administrator Guide

iDRAC9 — Server industry leading Embedded Management solution
7 In-band or out-of-band: Advantages of iDRAC and iSM compared to OMSA | ID 423
2.2 OpenManage Server Administrator (OMSA)
OpenManage Server Administrator provides a comprehensive one-one systems management solution for
both local and remote servers, their storage controllers, and Direct Attached Storage (DAS). OMSA can
provide this support by being installed in the operating system or hypervisor on a PowerEdge server.
While OMSA provides many of the same functions as iDRAC, it does have some limited functionality. OMSA
supports only legacy OM CLI for scripting options and not newer automation paradigms like Redfish. OMSA
does provide a few storage information (see chart below) that is still not available by using iSM or iDRAC. For
certain customers, that is a reason to continue using OMSA. These features and options are fully described in
the following matrix.
2.3 Limitations that are related to agent-based systems management
While many customers use the agent-based “in-band” agent for managing their servers, there are some
“understood” disadvantages associated with this process. The key implication is that the server has a
functioning agent in a functional operating system. Both items are necessary to check and report on the
overall health of network and storage devices. Some of other challenges in agent-based systems
management are depicted below.
Possible limitations and drawbacks of an in-band agent
Consuming Resources
The agent running on the host is often heavy-weight and consumes important
cycles like memory and CPU.
Host operating system
stop responding
If the host operating system stops responding, information about storage,
networking, and more is not available, along with the option to alert on any
issues.
Agent crash
Should the agent crash, or even while during an update, devices such as
storage, memory, and networking are not managed.
Multiple agents
While some agents are necessary, “the less the better” rule applies here.
Operating system-
dependent settings
Various operating system-dependent settings like BIOS cannot be modified.
2.4 Advantages of out of band management
Aside from the various points listed above, there are also many other features that out of band management
provides, as seen in the following table.
Feature
Benefit
Single source of
information
No need for multiple agents, or open “vendor specific” consoles to check health
status, perform configuration or update tasks.
Improve system
performance.
With no agent running on the host, there is no performance impact on the
server. This option allows the processors and memory to be dedicated solely to
supporting the operating system and applications, and not the management of
the server.
“Always on”
management
Out of band provides full functionality for all aspects of server management
independent of operating system presence or state. In other words, full
management at the ‘bare metal’ stage or if the operating system or hypervisor
is in a ‘stopped responding’ state. Also, IT admins have access to a system in
failed state to recover and troubleshoot the host operating system.