Chapter 13. Configuring I/O for Raw Partitions
/dev/rawinterface bypasses the kernel's block buffer cache entirely that is normally associated with block devices and goes right to the low level device itself. By bypassing the cache it accesses a physical device directly which allows applications such as Oracle databases to have more control over the I/O to the physical device. In fact, Oracle does it is own data caching and raw devices allow Oracle to ensure that data gets written to the disk immediately without OS caching.
O_DIRECTflag, thus bypasses the OS cache. Support for raw devices was reinstated in Red Hat Enterprise Linux 5.4 and later.
/dev/sdbcan change to
/dev/sdaif the scan order of the controllers is not configured. To force the scan order of the controllers, aliases can be set in
/etc/modprobe.conf. For example:
alias scsi_hostadapter1 aic7xxx
alias scsi_hostadapter2 lpfc