After installing a 64-bit version of Symantec Protection Engine (SPE) and configuring SPE to utilize the maximum amount of memory allowed performance seems to have decreased.
Symantec Protection Engine (SPE) defines the maximum memory space it can process files through the setting: InMemoryFileSystemSize. Symantec Protection Engine documentation states the maximum size is for this value is 4096. Using the XMLModifer tool allows setting the value to 4096 without generating an error.
64-Bit versions of SPE:
Setting the InMemoryFileSystemSize value to "4096" will result in files smaller than expected being written to disk instead of being processed in memory. This will increase Disk IO and can lead to longer duration scans. Under very heavy load it could potentially saturate the HDD / Array.
This issue is currently under investigation. This article will be updated once new information becomes available.
As a workaround to this issue utilize the commandline reference guide for your specific product version to set InMemoryFileSystemSize to the value of 4095.