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From "Myrna van Lunteren (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-2020) Change file option for syncing log file to disk from rws to rwd
Date Tue, 05 Jun 2007 19:04:26 GMT

    [ https://issues.apache.org/jira/browse/DERBY-2020?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12501657

Myrna van Lunteren commented on DERBY-2020:

I've tested 10.3 on Mac (OSX 10.4) for a bit, and all seems to work fine.
(except of running out of memory with suites.All, which is not unique to mac).

But then, the jvm version I'm running with does not have the JVM bug anymore.
So I can't verify the workaround is still in place.

I think it is ok to set this one to fixed.

> Change file option for syncing log file to disk from rws to rwd
> ---------------------------------------------------------------
>                 Key: DERBY-2020
>                 URL: https://issues.apache.org/jira/browse/DERBY-2020
>             Project: Derby
>          Issue Type: Improvement
>          Components: Performance, Store
>    Affects Versions:
>            Reporter: Olav Sandstaa
>            Assignee: Olav Sandstaa
>             Fix For:
>         Attachments: disk-cache.png, jvmsyncbug.diff, jvmsyncbug.stat, jvmsyncbug_v2.diff,
jvmsyncbug_v2.stat, jvmsyncbug_v3.diff, jvmsyncbug_v3.stat, no-disk-cache.png, rwd.diff, rwd.stat,
rwd_pre.diff, rwd_pre.stat, rwd_v2.diff
> For writing the transaction log to disk Derby uses a
> RandomAccessFile. If it is supported by the JVM, the log files are
> opened in "rws" mode making the file system take care of syncing
> writes to disk. "rws" mode will ensure that both the data and the file
> meta-data is updated for every write to the file. On some operating
> systems (e.g. Solaris) this leads to two write operation to the disk
> for every write issued by Derby. This is limiting the throughput of
> update intensive applications.  If we could change the file mode to
> "rwd" this could reduce the number of updates to the disk.
> I have run some simple tests where I have changed mode from "rws" to
> "rwd" for the Derby log file. When running a small numbers of
> concurrent client threads the throughput is almost doubled and the
> response time is almost halved. I will attach some graphs that show
> this when running a given number of concurrent "tpc-b" like clients. These
> graphs show the throughput when running with "rws" and "rwd" mode when the
> disk's write cache has been enabled and disabled.
> I am creating this Jira to have a place where we can collect
> information about issues both for and against changing the default
> mode for writing to log files.

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