[Ocfs2-users] Re: ocfs Vs ocfs2

[GOKHAN]

coreutils-4.5.3-26 is installed on RH3
----------------
RH3:
more /etc/issue
Red Hat Enterprise Linux AS release 3 (Taroon Update 2) 
uname -a
Linux dbcluster7 2.4.21-40.EL #1 SMP Thu Feb 2 22:12:47 EST 2006 ia64 ia64 ia64 GNU/Linux
---------------



Message: 7
Date: Wed, 17 Jan 2007 02:06:37 -0800 (PST)
From: Luis Freitas <lfreitas34 at yahoo.com>
Subject: Re: [Ocfs2-users] ocfs Vs ocfs2
To: ocfs2-users at oss.oracle.com, ocfs-users at oss.oracle.com
Message-ID: <706536.16119.qm at web51412.mail.yahoo.com>
Content-Type: text/plain; charset="iso-8859-1"

Joel,
   
     It is not using o_direct only if the coreutils package was not installed on the RH3.0 machine. (coreutils-4.5.3-41.i386.rpm ).
   
  http://oss.oracle.com/projects/coreutils/files/
   
     If it is installed, then both tests are using O_DIRECT, and can be compared.
   
     I do not have both a OCFS and a OCFS2 environment to compare here, but I am perceiving too a very slow performance with copy operations on the OCFS2 volume, compared to what I was used to in OCFS.
  
Regards,
  Luis
  
Joel Becker <Joel.Becker at oracle.com> wrote:
  On Tue, Jan 16, 2007 at 01:28:41AM -0800, GOKHAN wrote:
> Hi everbody this is my first post,
> I have two test server .(Both of them is idle)
> db1 : RHEL4 OCFS2
> db2 : RHEL3 OCFS
> 
> I test the IO both of them
> The result is below.
> 
> db1(Time Spend)db2(Time Spend)OS Test Command
> dd (1GB) (Yazma)0m0.796s0m18.420stime dd if=/dev/zero of=./sill.t bs=1M count=1000
> dd (1GB) (Okuma)0m0.241s8m16.406stime dd of=/dev/zero if=./sill.t bs=1M count=1000
> cp (1GB)0m0.986s7m32.452stime cp sill.t sill2.t

You are using dd(1), which does not use O_DIRECT. The original
ocfs (on 2.4 kernels) does not really support buffered I/O well. What
you are seeing is ocfs2 taking much better care of your buffered I/Os.
They will be consistent across the cluster. In the ocfs case, you are
caching a lot more because these safety precautions aren't taken.
HOWEVER, the most important factor is that you are not using
O_DIRECT. When you actually run the database, you _will_ be using
O_DIRECT (make sure to mount ocfs2 with '-o datavolume'). Without the
OS caching in the way, both filesystems should run at the same speed.
The upshot is that buffered I/O operations (such as plain dd(1))
are often not good indicators of database speed.

Joel

-- 

"To announce that there must be no criticism of them president, or
that we are to stand by the president, right or wrong, is not only
unpatriotic and servile, but is morally treasonable to the American
public."
- Theodore Roosevelt

Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker at oracle.com
Phone: (650) 506-8127


 
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