By John Gruber
Brew yourself the best coffee. Try YES PLZ today — $5 off for DF readers.
Last month eWeek caused a bit of a stir after publishing this article by Matthew Rothenberg and “Nick de Plume”, wherein they reported that Mac OS X 10.2.2 would introduce a new journaling file system.
Now that 10.2.2 is out, who’s right?
If you look at the Mac OS X 10.2.2 release notes, you will see no mention of “journaling” whatsoever. Point to Gruber.
If you look at the Mac OS X Server 10.2.2 release notes, however, you will see this:
This update introduces the Journalling file system for Mac OS X. Search the Knowledge Base on “journaling” to find more information.
[The inconsistent spelling and capitalization is Apple’s, not mine. Also, at this writing, there isn’t anything in the KnowledgeBase about journaling other than the aforementioned note to search in the KnowledgeBase for more information about journaling. Lather, rinse, repeat.]
Point to eWeek.
So is there a brand-new journaling file system in 10.2.2 or not? The answer depends on what your definition of “file system” is.
In the traditional sense, a file system describes the low-level structure of the disk format itself; it’s the “FS” in the “HFS” and “UFS”. The journaling feature in 10.2.2 is not a new file system in this sense. It is just a journaling extension that sits atop the same HFS+ file system that’s been around since Mac OS 8.1.
The new definition of “file system” — popularized by Linux users, whose ext3 file system is a similar extension on top of the non-journaling ext2 format — includes not just the format itself, but the operating system code that drives it.
Is it a file system? Yes. Is it journaling? Yes. And, while only the Disk Utility application from Mac OS X Server exposes the journaling feature via a real interface, it’s reportedly available in the regular version of 10.2.2 via the command-line “diskutil” tool.
But is it a big deal? I don’t think so, at least not in 10.2.2. One problem is that there doesn’t yet seem to be any documentation detailing exactly what the benefits to HFS+ journaling are (or what type of information gets journaled in the first place). Whatever the capabilities, they certainly seem to fall short of Rothenberg and dePlume’s description:
Fresh on the heels of its “Jaguar” release of Mac OS X 10.2, Apple Computer Inc. is about to spring a new surprise for the Unix-based OS: A journaled file system designed to provide corporate Mac sites with a new, historical view of their data.
So, while I’m forced to admit Rothenberg and dePlume were right, that doesn’t mean they were accurate.