<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">Joel,<br><br> I stand corrected.<br><br>Regards,<br>Luis<br><br>--- On <b>Mon, 2/9/09, Joel Becker <i><Joel.Becker@oracle.com></i></b> wrote:<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;">From: Joel Becker <Joel.Becker@oracle.com><br>Subject: Re: [Ocfs2-users] ASM over OCFS2 vs. Standard locally managed tablespaces<br>To: "Luis Freitas" <lfreitas34@yahoo.com><br>Cc: "<ocfs2-users@oss.oracle.com>" <ocfs2-users@oss.oracle.com><br>Date: Monday, February 9, 2009, 3:25 PM<br><br><pre>On Mon, Feb 09, 2009 at 04:16:23AM -0800, Luis Freitas wrote:<br>> About the performance, ASM is said to have similar performance to raw<br>devices in a SAME layout, being tightly integrated to Oracle. OCFS2 has some<br>overheads that are inherent to a file system, like cache
management, locking,<br>context switching, so it is likely to use more CPU power than ASM. But I dont<br>remember any specific benchmark comparing those. <br><br> ocfs2 has performance equivalent to raw devices when using<br>O_DIRECT, which the database will do for its datafiles. We worked hard<br>at that from the beginning. You won't see filesystem overhead for the<br>O_DIRECT access. You only see the overhead of cache management, etc,<br>for cached (non-O_DIRECT) files, which isn't what you're worried about<br>for database performance.<br><br>> Also, keep in mind that when you use a filesystem you are using<br>part of the memory for the filesystem cache. When using RAW or ASM you would<br>need to allocate this memory to the block buffer in order to compare results.<br><br> Again, Oracle uses O_DIRECT for datafiles. This keeps the data<br>out of the filesystem cache. A single-node (non-RAC) database can use<br>the filesystem
cache, and that can cause benchmark discrepancies, but<br>we're talking about RAC here.<br><br>Joel<br><br>-- <br><br>To spot the expert, pick the one who predicts the job will take the<br>longest and cost the most.<br><br>Joel Becker<br>Principal Software Developer<br>Oracle<br>E-mail: joel.becker@oracle.com<br>Phone: (650) 506-8127<br></pre></blockquote></td></tr></table><br>