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Re: Raw device 8.1.7.4.0 Linux

From: Mladen Gogala <mgogala_at_adelphia.net>
Date: Mon, 08 Dec 2003 05:30:44 GMT
Message-Id: <pan.2003.12.08.05.31.12.25866@adelphia.net>


On Sun, 07 Dec 2003 18:36:50 -0800, Daniel Morgan wrote:

>
> What nightmare with raw devices? In my experience, mostly with AIX, they
> are a few mouse clicks and never a thought except that little
> calculation of how much free space to leave behind.

Well, it's very hard to get raw devices to autoextend or shrink, it is very hard to back them up, you cannot use tar or cpio and copying them to another disk is a real pain. Using raw devices mandates purchase of expensive 3rd party backup software (good luck with dd). Last but not least, creating raw devices is a privileged operations that involves SAs and, usually, cannot be done by a DBA. The only situation when raw devices are what you really, really want is when you have a RAC (in case of 8i, it's OPS). Should I say that all of the operations listed above are quite easy with an ordinary file system? You are on AIX, which comes with a native implementation of JFS. JFS supports both direct IO and async IO, which means that you can use ordinary files with the same efficiency as raw devices. Have you ever benchmarked JFS vs. raw on AIX? I haven't, but I'll buy you a pizza and a drink if the difference is significant.

-- 
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Received on Sun Dec 07 2003 - 23:30:44 CST

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