Hi Roopesh,
“Memory” in Component Details – Thresholds and Watches – Memory
Is defined as a watch and can be found the watch report as:
Model typerfc2790App - 1watches
Name hrStorageUtilization
Developer ID 0xc40000
Author
Last Modified Time:
Model Type rfc2790App
Data Type Real
Expression ( ( REAL( hrStorageUsed.# ) / REAL( hrStorageSize.# ) ) * 100 )
Instance All
Active By Default Yes
Evaluate On Demand
Inheritable No
Threshold None
“Physical Memory” in Component Details – System Resources – File Systems - File Systems (RFC 2790)
Is defined as
Memory: RFC-2790
hrStorageType/0xc40783 - 1.3.6.1.2.1.25.2.3.1.2 hrStorageAllocationUnits/0xc4073b - 1.3.6.1.2.1.25.2.3.1.4 hrStorageSize/0xc4073c - 1.3.6.1.2.1.25.2.3.1.5 hrStorageUsed/0xc4073d - 1.3.6.1.2.1.25.2.3.1.6
Calculation:
Mem Free: (hrStorageSize * hrStorageAllocationUnits) · (hrStorageUsed * hrStorageAllocatioUnits)
Mem Used: hrStorageUsed * hrStorageAllocatioUnits
Utilization: used / (free + used )
**Note: hrStorageType is used to locate the specific entry which relates to physical RAM. hrStorage table also provide usitilzation information for virtual memory and file systems. We do not want these so we filter them out. If the value of hrStorageType is ·1.3.6.1.2.1.25.2.1.2· then we will use the same index across all attributes (ie if that value is found at position 2, then we will use the allocation units, size and used values at the same index).
The calculations are very similar if both are using the same source (RFC-2790), however there are other cases where different sources could be used such as UCDavisSNMPApp (NetSNMP) which is selected during discovery under “Memory” in Component Details – Thresholds and Watches – Memory but RFC-2790 will always use RFC-2790.
As to which is best to use to monitor is more of a personal preference. Monitoring memory on Linux servers is extremely difficult due to the way the OS caches memory and as such would provide false memory usage allocations, therefore Spectrum gives the users this flexibility to decide which is best for them.
On top of that you can use Attribute Redirection to further customize on how you want to monitor by using different mib objects.
I hope this helps,
Glenn