[Ocfs2-users] Re: ocfs Vs ocfs2

[Steffen Roegner]

GOKHAN wrote:
>
> coreutils-4.5.3-26 is installed on RH3
>
It is a bit more work than just having it installed:

'man dd' will tell you this:
       --o_direct
              Use  O_DIRECT file access. Mainly for use with FSâs That 
support O_DIRECT access.  There  are  three  forms  --o_direct  (selects
              default block size) --o_direct=<r/w block size> (use given 
block size for read and write operations)
              --o_direct=<read>,<write> (use specific block size  reads 
and writes)
              For the purposes of handling data between FSâs that  do  
and  do not  handle O_DIRECT access, the special value, 0, dictates that
              access will be via NON O_DIRECT means. This is  mainly  
for  use with stdin/stdout. eg, dd --o_direct=8192,0 if=/ocfs/file | 
gzip > /tmp/backup.gz

So, the command you would probably want to try would look like this:
'dd --o_direct of=/dev/zero if=./sill.t bs=1M count=1000'
But don't get too excited, I would still not expect it too be as fast as 
ocfs2.

hth
Steffen
>
> ----------------
>
> 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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> Try it now.
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