Oracle and raw devices on linux

Since RedHat Enterprise Linux version 5, raw devices are deprecated. According to this online manpage of raw(8). It states raw devices will exist for the life of RedHat Enterprise Linux 5.

Traditionally, raw (character) devices are used in cluster setups to be able to talk directly to disk devices (meaning no local buffering/caching takes place, which could corrupt cluster state advertising). The manpage also states:

If your application performs device access using this interface, Red Hat encourages you to modify your application to open the block device with the O_DIRECT flag.

This is exactly what is possible since database version according to metalink note 357492.1; “Linux 2.6 Kernel Deprecation Of Raw Devices”. This means the blockdevice can be used, instead of /dev/raw/rawn. It’s also possible for the clusterware to use the blockdevice instead of raw. I’ve only tested it with the clusterware version 11.

I’ve updated the RAC on VMware article to use the blockdevices.

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