Re: Raw Devices v.s. File System

From: Gaja Krishna Vaidyanatha <gajav_at_yahoo.com>
Date: Tue, 11 Jul 2000 13:09:04 -0700 (PDT)
Message-Id: <10555.111715@fatcity.com>

Michael,

If you are not running Oracle Parallel Server, believe me when I tell you that you will get comparable performance using Veritas vxfs file systems as compared to Raw Devices. There have been enough benchmarks and real-life production configurations that have been done to prove this. Been there...done that. It is not worth dealing with "raw devices" if you have an advanced file system such as Veritas with an I/O driver that facilitates "non-buffered I/O". This takes care of the "double buffering" problem that is prevelant with normal ufs filesystems.

In addition to configuring vxfs filesystems you need to install and configure the "Database Accelerator" - "Quick I/O for Oracle" component of Veritas. This simulates the effects of "non-buffered I/O". Basically, while configuring the file systems, the Quick I-O tag is put on it (so to speak) and this assists the driver in identifying "Quick I/O" calls to that filesystem and intercepting it. It does it by "bypassing" the file system buffercache and performing it directly from the device. So you have "raw device" comparable performance, without sacrificing the benefits of a cooked filesystem.

To minimize the overhead in filesystem-database block size mapping, keep the vxfs filesystem block size (default 8k) and the db_block_size of the database to the same. Then configure your Oracle database, just as usual. Leave the rest to Quick I/O, it does pretty well. There are white papers at www.veritas.com on Quick I/O and Oracle and how it works.

Cheers,

Gaja.

• Michael Johnson <mjohnson138_at_yahoo.com> wrote:
  > Hi there, another newbie question for the gurus.
  >
  > I will be running Oracle 8i on Solaris 8 and was
  > wondering about other's experiences and opinions about
  > raw devices v.s. the file system.
  >
  > From the Administrator's Reference, there may be
  > problems with ULIMIT and moving data files around.
  > Has anyone else experienced trouble? Anything I
  > should beware of?
  >
  > As always, thx.
  >
  > MJ
  >
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Gaja Krishna Vaidyanatha
Director, I-O Management Products
Quest Software Inc.
(972)-304-1170
gajav_at_yahoo.com

"Opinions and views expressed are my own and not of Quest"

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Do You Yahoo!? Received on Tue Jul 11 2000 - 15:09:04 CDT