A few metrics to evaluate feature usage and suggest improvements. Thanks to sureshms for some of these suggestions.
- Number of times a block in memory was read (before being ejected)
- Average block size for data written to memory tier
- Time the block was in memory before being ejected
- Number of blocks written to memory
- Number of memory writes requested but not satisfied (failed-over to disk)
- Number of blocks evicted without ever being read from memory
- Average delay between memory write and disk write (window where a node restart could cause data loss).
- Replicas written to disk by lazy writer
- Bytes written to disk by lazy writer
- Replicas deleted by application before being persisted to disk