This message is from the T13 list server.
Hale Landis wrote:
Having worked on caching algrorithms for various types of storage
devices for something like 30 years, I find this discussion a little
strange. I've never heard anyone describe "reading ahead" or "staging"
data to be something different from data "caching" and/or something that
is not part of a well designed data caching algorithm.
Maybe I come from a different background, but "read cache" and "read
ahead" are two different beasts from my perspective.
Read-ahead normally describes an -active- action, pre-loading sectors
into the cache in anticipation of a future event (further sequential reads).
Read caching normally describes a -passive- activity where the device
caches recently-read blocks, be they pre-loaded (read-ahead) sectors or
recently used (read-through / write-through / write-back) sectors.
Read ahead could be thought of as a subset of read caching, but there is
the active/passive difference that makes it not quite a pure subset.
Jeff
