Redis Memory Metrics group contains memory consumption related information as reported by the Redis instance running on each node.
- Used Memory: This is the total memory in megabytes allocated by Redis using its allocator (either standard libc, jemalloc, or an alternative allocator such as tcmalloc).
- Used Memory Rss: This is the memory in megabytes that Redis allocated as seen by the operating system (a.k.a resident set size). This is the number reported by tools such as top(1) and ps(1).
- Memory Fragmentation Ratio: This is the ratio between Used Memory Rss and Used Memory. A fragmentation ratio less than 1.0 means that Redis requires more memory than is available on the system and so it has resorted to using swap memory resources. A fragmentation ratio greater than 1.0 indicates that fragmentation is taking place and the Redis instance is consuming more physical memory than has been requested. A healthy Redis server Memory fragmentation ratio is slightly more than 1.0. A ratio greater than 1.5 indicates that excessive fragmentation is taking place.