Archive for January, 2008

Oracle and raw devices on linux

Wednesday, January 9th, 2008

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 10.1.2.0.2 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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Oprofile and VMware

Monday, January 7th, 2008

Do not work together.

Oprofile is a system-wide profiler for linux. VMware is the virtualisation software by the company with the same name.

I’ve installed Oprofile on a Centos 5.1 virtual machine in VMware server (formerly known as GSX server), and try to get profile data. Nope. Nothing. Some investigation on the internet reveals that others already encountered this problem. Oprofile doesn’t work in a vmware-virtualised linux box. According to the search results, this also is the case with machines on ESX server.

Well, VMware server just runs as some processes on a physical machine. Why not try there? Using debian 4.0 aka “etch”…
Wrong again! Oprofile seems to run fine (meaning a kernel module is loaded and a daemon is started) and I can get results…but the running VMware virtual machines crash and are not startable anymore, until I shutdown Oprofile.

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Installation of 11G RAC with ASM on two VMware virtual machines

Wednesday, January 2nd, 2008

Installation instructions: http://frits.homelinux.com/RAC11g_and_ASM_on_VMware.pdf
Comments are welcome!

The purpose of this instruction is to be able to have a working 11g RAC with ASM on a laptop. This enables consultants to have a RAC cluster for demo, development and test. Of course this setup is not supported (!)

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