Jim Smith wrote:
> Oracle: (my main experience)
> At various times Oracle have claimed (talking to consultants, not
> marketers) that raw devices are 5-20% faster than filesystems. This may
> vary on the current state of the oracle code and/or the filesystem being
> compared against. Veritas seem to agree by producing QuickIO for Oracle,
> claiming "performance of raw with the management of filesystem".

Well, I have been using the Veritas VxFS Quick I/O feature on Informix
7.31 and 9.20 for a couple of years now. On my system running on heavy
OLTP load and large number of buffers, I get about 5x shorter checkpoint
times on VxFS with QIO, compared to cooked chunks on 'plain' Veritas
VxFS file system. And yes, LRU_MAX_DIRTY/LRU_MIN_DIRTY values are
already at 1/0.

QIO is essentially a normal file system which allows you to access the
space reserved by a file through a character special device. So on
Informix, you can use KAIO even on top of a file system.
--
Toni