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Re: filesystem dbfile vs raw device dbfile

From: Nuno Souto <nsouto_at_nsw.bigpond.net.au.nospam>
Date: Mon, 19 Feb 2001 08:10:05 GMT
Message-ID: <3a90d0fc.2153324@news-server>

On Sun, 18 Feb 2001 16:57:34 -0600, "Spencer" <spencerp_at_swbell.net> wrote:

>on HP-UX, by using "raw" instead of file system files, Oracle
>can use asynchronous i/o (via the ascync driver), and avoid
>the overhead/bottlenecks associated with a file system. any
>improvement in performance will likely be unnoticeable on a
>lightly loaded system, and less than 10% under a heavy load.

Depends. *If* you installed all the patches that make all that work, *if* you setup everything the right way, *if* your filesystem cache hit pattern matches what your database applications are doing, *then* you *may* get less than 10% diff under heavy load.

IME, you get in any given UNIX system around 30% less CPU usage (that's right, CPU) when going raw, assuming that you were on standard "vanilla" file systems to start with. Of course, if you are patient enough to chase up all the patches needed (both ORACLE and UNIX), then it may pay off to go async I/O and ignore raw. But it takes a while to get everything pointed the right way...

Problem is that too many measure the wrong things when comparing raw to file system. (not saying you do, just making a general comment).

>
>while some tout the inability to use standard os commands to
>manipulate raw partitions as a "disadvantage", i actually find
>this to be an "advantage" of raw partitions. for example, the
>"rm" command cannot be used to remove a raw partition from
>the system.
>

Good point.

Cheers
Nuno Souto
nsouto_at_bigpond.net.au.nospam
http://www.users.bigpond.net.au/the_Den/index.html Received on Mon Feb 19 2001 - 02:10:05 CST

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