SOSS version 5 uses additional memory of about 650 bytes per object to support advanced features not available in version 4, such as property-based query and remote store access. Version 5 also expands its use of data partitioning, internal hash tables, and memory buffers to maximize performance on large clusters of multi-core systems.
The relative impact of these changes is significantly larger for very small object sizes. Very small objects incur more per-object overhead and make less efficient use of internal memory buffers. For example, 500K objects of size 940B (about 472MB total) require about 2.6GB of total process memory in version 4 and 3.55GB in version 5, an increase of about 37%. However, this same memory size using 50K objects which are 10X larger requires 800MB on version 4 and 970MB in version 5, a much smaller process size and an increase of only 22%.