Got a tip for us?
Let us know
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Journaling: Yes or No?
- Thread starter amc382
- Start date
- Sort by reaction score
Go on! Enable it!
It didn't save my data, though. Sad story happened two days ago.
Didn't wake up - reboot - disk unrecoverable - intialisation - clean install.
It didn't save my data, though. Sad story happened two days ago.
Didn't wake up - reboot - disk unrecoverable - intialisation - clean install.
i have heard a pretty good amount of talk about journaling as this wonderful feature in 10.3, but i am ashamed to say that i don't really understand what it does or what services it provides. could someone please enlighten me?
also, do your suggestions for enabling it apply even on slower HDs?
sorry to kinda hijack, and thanks for any info.
also, do your suggestions for enabling it apply even on slower HDs?
sorry to kinda hijack, and thanks for any info.
i know very little about journaling as well, so i'd also welcome more thorough description.
anyway, afaik, journaling basically keeps track of each and every file that's on the HD. this makes file system checks mostly unnecessary, thus making the start up faster...
anyway, afaik, journaling basically keeps track of each and every file that's on the HD. this makes file system checks mostly unnecessary, thus making the start up faster...
Journaling creates noticeable lag when moving any data around in the filesystem on my 4200rpm Powerbook drive. It makes no noticeable difference on my 7200rpm external firewire drive.
In short, journaling keeps track of diffs on your filesystem. When you initiate a disk write, the journaling subsystem notes the current state of the bits about to be overwritten and the changes to be made. Then the actual disk write happens.
If something happens before the actual write occurs, the journal has the record of the change - the journal is checked upon reboot and the changes are written. This mostly (but not completely) eliminates the possibility of disk corruption.
It does slow things down a little, but for most disk writes (editing files etc.) very little on the disk actually changes. The journal only need to track the changes, so it's not going to slow things down too much. Also, most journaling systems have a cache and write the file updates in bulk to the disk every X seconds (I know the ext3 filesystem uses X=5 by default; don't know much of anything about HFS+ journaling yet). Note that the journal log writes are not cached - it's the file updates themselves that are.
Edit: I couldn't find an article specific to HFS+ journaling, but here's one that talks about various Linux filesystems: http://www.cafecomputer.com/journaling.htm
If something happens before the actual write occurs, the journal has the record of the change - the journal is checked upon reboot and the changes are written. This mostly (but not completely) eliminates the possibility of disk corruption.
It does slow things down a little, but for most disk writes (editing files etc.) very little on the disk actually changes. The journal only need to track the changes, so it's not going to slow things down too much. Also, most journaling systems have a cache and write the file updates in bulk to the disk every X seconds (I know the ext3 filesystem uses X=5 by default; don't know much of anything about HFS+ journaling yet). Note that the journal log writes are not cached - it's the file updates themselves that are.
Edit: I couldn't find an article specific to HFS+ journaling, but here's one that talks about various Linux filesystems: http://www.cafecomputer.com/journaling.htm