RE: Slow read on OCFS Windows

  • From: "Marquez, Chris" <cmarquez@xxxxxxxxxxxxxxxx>
  • To: <stmontgo@xxxxxxxxx>, <Oracle-L@xxxxxxxxxxxxx>
  • Date: Thu, 12 May 2005 14:40:18 -0400

Didn't know they had ocfs for Windows!?

I use (have only used) ocfs on Linux.
It works, but is IMHO much slower than EXT3 and RAW.

>>Can anyone confirm if this copy attempt is expected behavior
What do you mean by "copy".
In the OCFS-Linux world "copy" can not / should not be done by "cp"
but rather by using the o_direct as part of the OCFS utils; 
cp --o_direct=yes /o04/arch/orcl/arch_orcl_T1_S136.arc  /o01/arch/

Copying files (i.e. cp --o_direct ..., dd o_direct=yes ..., tar --o_direct ...) 
from an OCFS partition requires the application of fileutils and tar patches 
that provide direct_io write capability. o_direct enabled versions of these 
utilities are available from MetaLink  ( as patches:

    * Patch 2883583: fileutils-4.1-4.2.i386.rpm 
    * Patch 2913284: tar-1.13.25-9.i386.rpm

Update on OCFS
by Wim Coekaerts 

When the database opens a file on OCFS, it opens it with an extra flag, 
O_DIRECT. When a file on any node is opened with O_DIRECT, regular file access 
is not allowed. Attempting a cp, an md5sum, or a dd through the standard OS 
tools will fail with -EPERM. If you want to be able to use cp or dd while the 
database is up and running?to make a hot backup, for instance?you need to 
download updated fileutils packages or use RMAN.

These updated fileutils?cp, dd, and the like?take an option, o_direct=yes, that 
makes the tool also use 0_direct when opening the file.

Using O_direct makes the filesystem perform better. If you want to use dd or 
cp, you should also add a large blocksize; the ideal size for OCFS is between 
512K and 1MB. For example:

dd o_direct=yes if=/ocfs/foo of=/backup/foo.bak bs=1M 


Chris Marquez
Oracle DBA
HEYMONitor? -
"Oracle Monitoring & Alerting Solution"

-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx on behalf of Steve Montgomery
Sent: Thu 5/12/2005 1:56 PM
To: Oracle-L@xxxxxxxxxxxxx
Subject: Slow read on OCFS Windows
We are recovering from a SAN failure as we put things back together=20
we notice that copying database files from NFTS on one server to OCFS
on the Windooze cluster fails, even a 1 k file. We can copy by pulling
the files to the OCFS lun ok then . I'm suspicious that the SAN is not
completetly healthy. Can anyone confirm if this copy attempt is
expected behavior. SAN is CX 600 btw




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