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Method for dynamically adjusting file system log based on historical usage data

IP.com Disclosure Number: IPCOM000203075D
Publication Date: 2011-Jan-18
Document File: 2 page(s) / 21K

Publishing Venue

The IP.com Prior Art Database

Abstract

A system and method for dynamically adjusting a journaled file system log based on historical usage data is disclosed.

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Method for dynamically adjusting file system log based on historical usage data

Disclosed is a system and method for dynamically adjusting a journaled file system log based on historical usage data.

When a journaled filed system is created, the size of the log is set at creation time. However, the usage of the log depends on the nature and the amount of activity in the file system. Since writes to the file system are first written to the log, those file systems that have significant updates utilize more log space than those that are written and then mainly read. For this reason, highly active file systems such as those used by web-servers of dynamic html pages need larger logs than file systems that are mostly read only.

Current implementations of journaled file systems take steps to prevent "log wrap." Log wrap is a fatal condition where the log fills up. This is done by holding all new transactions until file system metadata can be written to disk and portions of the log emptied. If the log is too small for the kind of activity in the file system this condition occurs repeatedly, at the expense of overall performance. When this occurs too frequently, it is an indication that the size of the log needs to be increased. Conversely, if the activity in a file system never results in log usage greater than a certain percentage, then that space is wasted. There is no external indication for the "too big" state. In addition it would require significant monitoring to determine the "too big" case manually.

At file system creation time, there is no known way to accurately predict the optimal size of the log. If the size turns out to be inapprop...