[ First posted on www.lafcpug.org, November 16, 2003. ]
I'm a post-production consultant to a variety of broadcast and film
production studios throughout Hollywood. In dealing with my clients,
their number one concern is maximizing the performance of their equipment,
while maintaining the highest level of data integrity.
New to most of us with OS X 10.3 is File Journaling. First released
by Apple in OS X Server 10.2, this new feature has a direct impact
on how we get maximum performance with maximum safety for our editing
systems.
According to Apple's web site: "Journaling is a technique that
helps protect the integrity of the Mac OS Extended file systems on
Mac OS X volumes. It both prevents a disk from getting into an inconsistent
state and expedites disk repair if the server fails.
"When you enable journaling on a disk, a continuous record of changes
to files on the disk is maintained in the journal. If your computer
stops because of a power failure or some other issue, the journal is
used to restore the disk to a known-good state when the server restarts.
"With journaling turned on, the file system logs transactions
as they occur. If the server fails in the middle of an operation, the
file system can 'replay' the information in its log and complete the operation
when the server restarts."
Basically, Unix, in order to get improved performance, keeps disk directories
in memory and only periodically writes them to your hard disk. If you
crash, your directories are, in almost all cases, out of sync with
the files recorded on your hard drives.
Many of us, faced with a system crash, will use FSCK (or, if the situation
is really bad, Disk Warrior X) to rebuild our directories. However,
with OS X 10.3, FSCK no longer works the way it did in 10.2. In fact,
it doesn't work at all. This is because file journaling is turned on
by default in OS X 10.3.
When journaling is turned on, every time you write a file to your hard
disk, or modify an existing file, the operating system writes an entry
into a transaction file. This is MUCH quicker than writing out the
full directory structure.
Journaling is also much safer for your data because if you crash, the
operating system uses the journal to update the directory structure,
which means far less lost data and far faster reboots.
The problem is that journaling takes time. Enough time that it is worth
considering turning journaling off on all your media drives. The benefit
is that you get faster performance. The disadvantage is that in the
event of a crash, you don't have the protection journaling provides.
On the third hand, hard drives with journaling turned off are in no
worse shape than hard drives running under OS 10.2.
In my experience with a wide variety of media clients, disk directory
problems almost never arise with secondary drives, they are almost
exclusively the domain of the boot disk.
As Apple writes: "If your [computer] contains high-bandwidth usage
data files, such as large video, graphics, or audio files, you may
want to weigh the benefits of using journaling against the performance
needed to access your data. In most cases, the impact of journaling
upon data access performance are unnoticeable to users, but its implementation
may not be practical for [computers] where data access demands outweigh
its benefits.
My recommendation? Leave journaling turned on for your boot disk and
turn it off for all secondary drives (both internal and external) that
are used to store media files. For external drives that store data,
not media, turn journaling on.
Journaling is controlled using Disk Utility. And there are two ways
you can turn Journaling on (the default) or off (better for media drives).
First, is when you setup your drive by selecting the appropriate option
in the Erase tab.
However, you can also turn off journaling in the Disk Utility by selecting
your hard disk then going to File->Disable Journaling, which doesn't
involve reformatting your drive and erasing data.
For more technical information on File Journaling, read Article ID
107249 on the Apple Support web site.
Copyright © 2003, Larry Jordan
- - -
Larry Jordan is an Apple-Certified Trainer
in Digital Media with over 25 years experience as a producer, director
and editor. Based in Los Angeles,
he's a member of both the Directors Guild and Producers Guild. He's
been using Macintosh computers since January 24, 1984, and Final
Cut since version 1.0. You can reach
him at: larry@larryjordan.biz.
Click for a printer-friendly
version.
Larry Jordan is a post-production consultant and an Apple-Certified Trainer in Digital Media with over 25 years experience as producer, director and editor with network, local and corporate credits. Based in Los Angeles, he's a member of both the Directors Guild of America and the Producers Guild of America.
The information in this article is believed to be accurate at the time of publication. However, the author assumes no liability in case things go wrong. Please use your best judgment in applying these suggestions.
The opinions expressed in this article are solely those of the author. This newsletter has not been reviewed or sanctioned by Apple or any other third party. All trademarks are the property of their respective owners and are mentioned here for editorial purposes only.
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