How necessary is it to reserve 15% disk space?

[ElDiabloConCaca]

Originally Posted by Convert

I only have 6GB at the mo.

It's really odd. Everytime I wake up the laptop from it's forced sleep (still won't sleep when I close the lid) it's missing a few GB...

I think that's because Macintosh systems that support "deep sleep" operate similarly to Windows' "Hibernate" function -- that is, any data in RAM is written to the hard drive (so if you've got 1GB of RAM, I would assume about 1GB of data is written to disk, presuming all 1GB is being used) and electricity does not flow through certain systems (RAM, processor, etc.). When you wake up, the data is read back into RAM from the disk, and I don't know if it's erased after that or remains around a while afterward...

Can anyone confirm this?

[Viro]

Originally Posted by Mephisto

RacerX is it a problem on HFS as well or just HFS+? Does Apple admit to this problem? Is the root cause known? i.e. is it the autodefragging as an example.

It baffles the imagination that a problem of this nature has existed for years without correction or at least a safety net to prevent catastrophic data loss. I have no reason to doubt it though, a little searching shows that it is a commonly held opinion. Of course Apple does have a bit of history of ignoring problems in the hopes that they will go away. (iBook mainboard problems, the light spots on the LCD, etc...)

If you refer to the thread I pointed to at the start of this topic, you'll see that HFS was even worse than HFS+. No idea if Apple thinks this is a problem or not. It definitely is inconvenient and I wish Apple would move to a different filesystem.

[Mephisto]

I read it yesterday when you first posted it, then did further research to corroborate the statements. I saw the comments to the effect that HFS suffered from the same problems but saw little backing that up elsewhere. Given the average Apple user's use of voodoo mechanics to diagnose errors I asked someone who seems to have experience and technical ability (RacerX) his opinion. I do not doubt your technical ability but the fact that you asked the question tends to suggest to me that you have little useful to say in the matter.

I would rather see Apple correct the problem than dump HFS+. ReiserFS might be better but that does not mean porting the FS to Mac would not cause new problems. I have never been fond of dumping a technology just because it has a likely fixable flaw.

[Viro]

Yeap. I've got very little useful things to say on HFS+ since I've never really had reason to delve too deeply into the underlying kernel of OS X. What makes things more frustrating is the lack of documentation on Apple's part too. So unless someone goes through the Darwin source code, we may never know for certain.

[RacerX]

Originally Posted by Viro

What makes things more frustrating is the lack of documentation on Apple's part too.

Maybe this will help on the documentation side of things.

Originally Posted by Viro

IMHO, Apple should ditch HFS+ and use UFS. Sure, UFS on OS X is slow, but that's because it's v1 (or something ) instead of V2 as used by FreeBSD. Also, there's ReiserFS that's free and performs very well. It's also B-Tree based so that should make it more similar to HFS+.

The problem is legacy applications. Pretty much anything done using Carbon is going to require HFS+ (that includes the Finder). What is worse is that there is now enough mixing between Carbon and Cocoa that even Cocoa apps have enough Carbon calls to slow them down on anything other than HFS+.

As for the UFS that Apple is currently using, it was developed from NeXT's UFS. There were a number of versions, each different from the previous version. The first Rhapsody systems used a file system that was not compatible with OPENSTEP systems (and the PowerPC version was not compatible with the Intel version). Apple then made another step with the next release of Rhapsody, but hadn't gotten what they wanted (something like HFS+ was what they were aiming for). With the release of Mac OS X Server 1.0 (the first public version of Rhapsody) they ended development of their UFS and turned back to HFS+ with Mac OS X.

I love my Rhapsody systems (as most people know) but UFS (even after all of Apple's work with their version) is no where near as advanced as HFS+. I think Apple made the right choice. In the end the benefits of HFS/HFS+ far out weight the draw backs.

When discussing this with other consultants, the thing we would like to see Apple add to Mac OS X for now is a space warning when the disk is starting to fill into that danger zone.

Having read the thread that was linked, I would concur with their assessment... keeping in mind that the 15% rule is a soft limit and not a hard barrier.

My main system is short on space, it has two drives, 8 GB and 4 GB, and I have to burn stuff off or move things to my servers regularly. Still, I have a wonderful system that has had a perfect performance record over the last two and a half years. I have not had to do any maintenance on it at all. Yes, I sometimes run short of the 15% limit, but I try to not do it too often or for too long.

[Convert]

Down to 3GB this morning, now back up to 7GB. Rebooted to get a 'fresh' number, I have 4.13GB apparently. This is bugging me.

[adambyte]

Originally Posted by Viro

How necessary is it to reserve 15% disk space?

How necessary is it that you have your data?

[Viro]

Originally Posted by adambyte

How necessary is it that you have your data?

Now now, no need to be cheeky it turns out that 15% is a soft limit anyway, more like a recommendation than a requirement.