Disk caching


for slow disk performance


**Buffer cache (in memory)** : cache file blocks in memory to capture locality in buffer cache or buffer cache - Idea: cache file blocks in memory to capture locality in buffer cache (or buffer cache)
- this cache is system wide, shared by all processes
- cache consistency issues can be occur
**Page cache** - – Caches pages rather than disk blocks using virtual memory techniques. – Memory-mapped I/O uses a page cache.
**Unified Buffer cache** -– A unified buffer cache uses the same page cache to cache both memory-mapped pages and ordinary file system I/O. – Avoids double caching and the possibility of inconsistencies between page caches and buffer caches.
