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From "Olav Sandstaa (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-2020) Change file option for syncing log file to disk from rws to rwd
Date Wed, 25 Apr 2007 11:37:16 GMT

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

Olav Sandstaa updated DERBY-2020:
---------------------------------

    Attachment: rwd_pre.stat
                rwd_pre.diff

This patch (rwd_pre.diff) contains changes in comments and a method name that could be committed
independently and in advance of the actual change of file mode for log files. The main changes
are:

  1. Rename the method called supportsRws() to supportWriteSync() in WritableStorageFactory
and all of its implementation.

  2. Fixed code comments referring to "rws" to also include "rwd" so that the comments also
will be valid if rwd is used.

The patch does not include any functional changes. The purpose of submitting this separately
is to keep the size of the actual patch that changes the file mode small.

Derbyall and the Junit suite have been run with zero failures.

The patch is ready for review and commit.

> 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: 10.3.0.0
>            Reporter: Olav Sandstaa
>         Assigned To: Olav Sandstaa
>         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
>
>
> 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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