PRTG & The Exchange Admin (Part 4/6): Metrics That Matter: Memory

 Originally published on November 27, 2017 by Simon Bell
Last updated on March 03, 2022 • 8 minute read

Part 4 - Using PRTG's Memory Sensors

Here, in the fourth part of the series on how PRTG can help the Exchange Admin, we’re looking at more Metrics That Matter. This time concentrating memory specific counters – those concerned with memory allocation, consumption and paging.

Disclaimer - Obviously, the values seen in your deployment will vary depending on the architecture and size of the environment, and the available metrics may also depend on Exchange version in use, and the roles configured on the server.

Memory Counters




Memory\Available Mbytes


Shows the amount of physical memory, in megabytes (MB), immediately available for allocation to a process or for system use. It's equal to the sum of memory assigned to the standby (cached), free, and zero page lists.

Should remain above 100 MB at all times.

Memory\Pool Nonpaged bytes





Consists of system virtual addresses guaranteed to be resident in physical memory at all times and so can be accessed from any address space without any paging input/output (I/O). Like paged pool, nonpaged pool is created during system initialization and is used by kernel-mode components to allocate system memory.


Memory\Pool Paged bytes



Shows the portion of shared system memory that can be paged to the on-disk paging file. Paged pool is created during system initialization and is used by kernel-mode components to allocate system memory. 

Monitor for increases in pool paged bytes indicating a possible memory leak.


Memory\Cache Bytes





Shows the current size, in bytes, of the file system cache. By default, the cache uses up to 50% of available physical memory. The counter value is the sum of Memory\System Cache Resident Bytes, Memory\System Driver Resident Bytes, Memory\System Code Resident Bytes, and Memory\Pool Paged Resident Bytes.

Should remain steady after applications cache their memory usage. Check for large dips in this counter, which could be attributed to working set trimming and excessive paging.

Used by the content index catalog and continuous replication log copying.


Memory\Committed Bytes




Shows the amount of committed virtual memory, in bytes. Committed memory is the physical memory that has space reserved on the disk paging files. There can be one or more paging files on each physical drive.

This counter displays the last observed value only; it isn't an average.


Memory\%Committed Bytes in Use




Shows the ratio of Memory\Committed Bytes to the Memory\Commit Limit. Committed memory is the physical memory in use for which space has been reserved in the paging file should it need to be written to disk. 

The commit limit is determined by the size of the paging file. If the paging file is enlarged, the commit limit increases, and the ratio is reduced.

This counter displays the current percentage value only; it isn't an average. 

If this value is high (more than 90%), you may begin to see commit failures. This is a clear indication that the system is under memory pressure.



< 90%


Monitoring Exchange memory paging with PRTG

Memory Consumption Counters




Process(*)\Private Bytes

Shows the current number of bytes this process has allocated that can't be shared with other processes.

Process(*)\Virtual Bytes

Represents (in bytes) how much virtual address space the process is currently consuming.



These are the important Memory related metrics that can be used to determine the health and performance of an Exchange system. All of which can be easily and quickly checked using PRTG’s Custom Sensors, as we saw in the previous article Your Secret Weapon for Monitoring Exchange: Custom WMI, PerfMon and Script Sensors

Look out for more in this Exchange “Metrics That Matter” series where we’ll look at:

  • .NET Framework and Network
  • Exchange & Domain Controllers, Client Access Server
  • Monitoring different Exchange Roles

Check the other parts of the series here:

Part 1: 8 Out-Of-The-Box Exchange Sensors That Will Save Your @ss
Part 2: Your Secret Weapon for Monitoring Exchange: Custom WMI, PerfMon and Script Sensors
Part 3: Metrics That Matter: Processor and Process Metrics for MS Exchange