RSA Product Set: SecurID 
RSA Product/Service Type: Authentication Manager
RSA Version/Condition: 8.x
 

• RSA Authentication Manager ver. 8.x show free memory that is less than available memory.
• Some SNMP traps for high memory utilization can be triggered even when the system is idle. 

Do Linux free, vmstat and top commands accurately show the amount of free RAM?

Key Insight: The "free" memory in free and top is not the only usable memory. Linux uses unused RAM for buffers and cache to speed up disk operations. This memory is available for applications when needed, so "available" (from free) is the true measure of free RAM.

Linux uses a memory management known as "lazy man" memory mapping to speed up disk access. But this memory allocated for disk access is readily available to applications when needed. Therefore Linux commands such as free, top and vmstat show both used and available memory.

"Available" memory is the true measure of free RAM in the Linux on the RSA Authentication Manager Appliances.

In such a memory management/kernel approach, (scroll to the second to the last paragraph of the page on this link):

To make the most efficient use of real memory, Linux automatically uses all free RAM for buffer cache, but also automatically makes the cache smaller when programs need more memory.

Linux commands such as free, top and vmstat show both used and available memory.

 
"Available" memory is the true measure of free RAM in the Linux on the RSA Authentication Manager Appliances.

Use available memory as the most accurate indicator of free RAM for starting new applications on your AM appliance.

Use available memory as the most accurate indicator of free RAM for starting new applications on your AM appliance.

You can also use an SNMP OID for the trap vs free output.  For more information on SNMP traps on Linux, reference this article on Linux SNMP OIDs for CPU,Memory and Disk Statistics.

You should consider the use of the UCD OID .1.3.6.1.4.1.2021 for CPU and memory usage versus using HOST MIBs, noting all reported available thresholds report in kilobytes.

Authentication Manager 8.1 SNMP OIDs

• Total physical memory for the operating system memory in KB: .1.3.6.1.4.1.674.10892.1.400.20.1.5
• Available physical memory for the operating system memory in KB.: .1.3.6.1.4.1.674.10892.1.400.20.1.6

Complete list of UCD MIB OIDS for older RSA SecurID Appliance 3.0

For additional information on hardware SNMP traps for Authentication Manager 8.1 or the RSA SecurID Appliance 3.0, see the RSA Authentication Manager 8.1 SNMP Reference Guide, Revision 1 or the RSA SecurID Appliance 3.0 SNMP Reference Guide.