1. Component File Journaling Options
Richard Smith
14 September, 2009

2. Component file layout Free space Global file information (root)2 1
Free space
Global file information (root)
Component index blocks
Component data (APL arrays)
Free space nodes
Multiple file writes per update

3. 12.0 journaled update 2 1
Write journal to end of file, which describes the updates
Perform updates
Clear journal
If interrupted, the journal remains present so the update can be redone

4. Safer journaled updates2 2
Journaling does not work when disk caches are not flushed
Forcing data to be flushed to disk is slow but may be minimised by:
Using checksummed components
Using checksummed journal

5. No data loss on OS crash
Would require 4 disk cache flushes per update if no checksums
Can be achieved with 2 disk cache flushes per update using checksums
Can be achieved with 1 disk cache flush per update and repair tool
Repair tool can be used with any checksummed component file.

6. Journaling/checksum choices√ X X √ X √ ? √ ? √ ? √
Compatibility with 11.0 and earlier
Compatibility with 12.0
Availability in 12.1

7. Repair tool demo

8. Component File Journaling Options
Richard Smith
14 September, 2009