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From Mike Matrigali <mikem_...@sbcglobal.net>
Subject Re: java1.4.2 "rws" mode fix: LogToFile.java diff
Date Fri, 03 Sep 2004 16:21:58 GMT
Hash: SHA1

is your log preallocated or not?  Until darby switched to preallocated
non-growing files no performance gain was seen going to rws.  Little or
no difference was seen using rws vs rwd on linux and windows where it
was tested.

Are your writes block bounded?

Michael.Giroux@objectweb.org wrote:

| I have been developing a log facility specifically for Transaction
| XA Commit protocol.  The project (howl.objectweb.org) has been working
| toward a throughput target of 10,000 tx/sec to the journal.  I have tried
| both "rw" with appropriate force() calls and "rwd".  What I found is that
| the "rwd" mode is a little slower than "rw".  Difference depends on the
| type of disk.  On my 7200 rpm ATA drive, the "rwd" is almost 40% slower
| than "rw".  On my 10,000 rpm SATA drive, the "rwd" is only about 12%
| slower than "rw".
| The IO pattern is quite different for XA protocol than it will be for
| database logging, specifically, there are only two log records per
| XA commit, and the first one must be forced.
| I will be interested is hearing how "rwd" does with the Derby log.
| The HOWL logger will be used by Apache Geroninmo Transaction
| Manager and is being used by ActiveMq.  There may be an opportunity
| to apply lessons learned from our projects (Derby and HOWL) to
| both log facilities.
| Michael Giroux, Objectweb.org
| Jan Hlavaty <hlavac@code.cz> wrote on 09/03/2004 05:57:05 AM:
|>Steen Jansdal wrote:
|>>You are probably right. I don't know what mode I'm trying since I'm
|>>using the derby code unmodified. I just trying to tell you what I'm
|>>seeing with my file monitor. I'm not a derby expert, yet, so I don't
|>>now all the small technical details.
|>Yes, Derby code in org.apache.derby.impl.store.raw.log.LogToFile is
|>using "rws" mode heavily, and no "rwd" at all. I suggest we try "rwd"
|>and see if performance is improved.
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