buffer cache/chunk cache
XFS uses two levels of buffer cache:
- standard bufs (dev/block #) limited to 16K or 64K depending on page size. (can be pinned).
- Buffers physically point to VM pages
- standard bufs are used for meta data I/O.
- chunk cache clusters buffers (user data):
- collection of standard bufs (logically contiguous) per file
- not always associated with disk blocks (delayed allocate)
- supports large pages (16k, 64k, 256k, 1m, 4m, 16m)
- chunk cache buffers searched by file offset