Exchange administrators have to manage and monitor numerous facets of their servers so that their user community is never kept waiting for messages. It used to be that server administrators had to also manage settings that affected the memory usage of their systems. A couple of those settings involved the use of page files and virtual memory.

Virtual memory is a concept that has been around for some time. Systems are configured with memory whose size is the result of analysis, computations and sometimes a best-guess estimate of the memory requirements for the applications. When there is insufficient memory available in RAM to run an application then other areas of memory are paged out to disk space and later retrieved when needed. The paged memory that is stored on the disk drives is commonly referred to as a “swap file”. But the official terminology is to refer to this data as “virtual memory”.

Exchange Server is also an application with memory needs. And so Exchange Server also relies on virtual memory for its successful execution. Unfortunately just as a disk drive can get fragmented over time virtual memory can also get fragmented over time. And when virtual memory fragmentation happens then administrators, and their end users, will see degradation in the performance of Exchange Server.

Continue reading Troubleshooting Virtual Memory Fragmentation

Configuration of an email server involves many sizing considerations. One of those sizing considerations is called Virtual Memory. Virtual memory is used to temporarily swap operating system items in and out of memory during high memory usage periods. Swap space is usually set to be one to two times of available memory. The swap space consists of a swap file located on disk. All applications benefit from swap space as it allows the applications to run when otherwise they would be starved for memory. Exchange server as an application also benefits from virtual memory.

But the virtual memory blocks must be large enough to meet the needs of the memory requirements of the application processes. If the block sizes available are not large enough then the condition of virtual memory fragmentation occurs. Some of the causes can include the different duration times and different sizes of memory allocations that happen as a result of normal swap operations.

As time goes by large blocks of memory become harder to allocate and at some point will cause applications to fail. Warning and error messages are generated as the virtual memory space becomes more and more fragmented. Some of the warning messages can include event ID 9582 which will be logged in the application event log. This event does not mean that the situation has hit the critical stage but it can and it should be taken as a notification to review the swap file size and to monitor its usage.

The event ID 9582 can be recorded in the event log as follows:
 Source: MSExchangeIS
Category: Performance
ID: 9582
Type: Warning
Description: “The virtual memory necessary to run your Exchange server is fragmented in such a way that performance may be affected. It is highly recommended that you restart all Exchange services to correct this issue.”

This can occur if an Exchange server has less than 32MB of free contiguous virtual address space.

Continue reading Troubleshooting Virtual Memory Fragmentation