[CUBE] Panther Behavior

[Steve Goldstein]

At 8:47 AM -0600 1/26/04, Rod Clifford wrote:
>Did "fsck -y" in single use mode & was returned with with the 
>statement "fsck -f force"

Was this last one as written on your screen, or was it simply either 
"fsck -fy" or "fsck -f"?  The "f" means to force the file system 
check.  Your HDs are now journaled*, and fixing with fsck presumably 
wipes out the journaling.

>Is this typical performance? Jag loaded much faster (it seems).   Rod

Yes!


I copied this down from another member on one of these lists for my 
own reference, but I failed to copy his/her name.  I hope the author 
will forgive my sending the explanation along for you:

JOURNALING

One minor annoyance with journaling is that once a drive has been 
journaled, the "fsck -y" command you enter in Single User mode to run 
diagnostics will not work.  You'll have to use the "fsck -f" command 
to force checking the drive, but theoretically, one of the reasons 
for journaling is to reduce the need to run the fsck diagnostics. 
So, it's pretty much a wash at that point.
...
If you installed Panther, it will automatically journal the boot 
drive.  If you're on a machine with multiple hard drives (like a G4 
or G5 tower), open Disk Utility, select the volume you wish to 
journal, and click on the "Enable Journaling" button.  Your drive 
will be journaled, no need to erase the drive.
...
If you wish to disable journaling (let's say, for someone who works 
with iMovie, Final Cut Pro, or another disk-intensive application), 
select the journaled drive in Disk Utility, go to the File menu and 
choose "Disable Journaling."

Personally, I have all my drives journaled.  I don't run any 
disk-intensive apps, and the advantages of journaling (quicker boot 
times, data security) outweigh its disadvantages.  However, bear in 
mind that journaling "is not" a substitute for regular backups, it's 
just an added safety net against unforeseen circumstances that may 
cause data loss (power outages and component failures).

So, with a 3 pronged strategy of a journaled drive, regular backups 
(to protect against data loss), and an Uninterruptible Power Supply 
(to give you time to safely shut down your machine in the event of an 
outage), you should be pretty much protected against any situation. 
It's not a guarantee, but it's pretty close to it.

"Journaling" is a feature that helps protect the file system against 
power outages or hardware component failures, reducing the need for 
repairs.  Journaling was first introduced in Mac OS X Server 10.2.2, 
then to the non-server OS in Mac OS X 10.3 Panther.  This document 
explains some of the benefits of using this feature and how it works.

Journaling for the Mac OS Extended (HFS Plus) file system enhances 
computer availability and fault resilience, which is especially 
noteworthy for servers.  Journaling protects the integrity of the 
file system on Xserve and other computers using Mac OS X Server in 
the event of an unplanned shutdown or power failure.  It also helps 
to maximize the uptime of servers and connected storage devices by 
expediting repairs to the affected volumes when the system restarts.
...
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.
...
Journaled file system is part of a set of incremental enhancements to 
the Mac OS Extended file system, and it is backward compatible with 
the Mac OS Extended file system.  Users can read, write, and access 
journaled Mac OS Extended volumes on computers that do not have a 
journaling feature.

Most disk utilities designed to work with the Mac OS Extended file 
system can also be used when journaling is turned on. You should 
check with your disk utility vendor before using earlier disk 
utilities with a journaled file system.
...
If your server 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 servers where data access demands outweigh its 
benefits.

You can turn journaling on and off for disks on the server you are 
logged into by using Disk Utility or command line tools, with or 
without erasing the volume.  For instructions, see technical document 
107248: " Mac OS X Server 10.2: How to Enable/Disable Journaling or 
Repair a Journaled Volume ".