My explanation is that filesystem performance on desktop and laptop systems is not that big a deal; while on larger servers like what ZFS is targeted for, filesystem performance in all facets is very important.
hfs+ bears the marks of some decisions that made sense in the eighties, when macos was barely capable of running a single program at a time, but are limiting today. pretty much everything requires locking the volume catalog, which makes disk access almost single-threaded. add to this the fact that apple is not afraid to throw out old stuff and bring in new -- they chucked the entire operating system nine years ago -- and the fact that they are still using hfs+ seems very strange indeed.
the only thing i can figure is that they were grooming zfs as a successor, but it was taking longer than expected. now i guess they have to go back to the drawing board and think of something else.
"they chucked the entire operating system nine years ago"
It's not like they built another OS - NeXT had one ready to go - even ported to x86. IIRC, all previous attempts to write a new OS to succeed MacOS classic failed miserably.
What advantage NeXT brought is that it's a very modular OS. Unix programs, traditionally, don't look the OS from too close and that makes swapping file-systems easy. Or, at the very least, possible.
I'm running ext4 on my laptop. It is significantly faster than ext3. Cold Boot time is awesome. (Sorry HN - I should really test/validate/quantify this, If I get some spare time - I'll try it out and post it here)
Don't forget stuff like time machine is tied into some of Apple's FS hooks.
And of course the fact that the high end (apples market) is undergoing a pretty major shift in hard drive technology at the moment (SSD's).
Although performance is a nice feature, the most important things in ZFS are the zero-cost snapshots (very nice for backups, versioning etc) and redundancy and data corruption prevention. I love each and every file on my drive and I want their contents correct.
Oh but it is - Macs are often used for, say, video editing. SGI realized the importance of filesystem performance in this application space and developed XFS (which Apple could adopt easily) and GRIO.
It would be intensely difficult technically for Apple to port XFS (perhaps not as bad as the rewrite to make it actually use Linux's VFS instead of implementing its own). It's also GPL — never going to happen for that reason alone.
As a longtime XFS user, I can tell you that it has pathological problems when used anywhere near a user's desktop: unlinking is abysmally slow (and even worse under rm -R). It also has a habit of delaying flush for way too long, both using up piles of kernel memory and making itself extremely vulnerable to power loss.
SGI has the full copyright to the version they initially released, but modern XFS has spent 8 years getting integrated into Linux by many independent contributors.
Oh please, apple is the worst file-system designer on the planet. HFS, HFS+ and what not. Wastes tonnes of space (space allocation+journalling) and i'd rather use FAT, atleast it is compatible with other operating systems.
Apple should stick to fancy buttons and animation thanks.
My explanation is that filesystem performance on desktop and laptop systems is not that big a deal; while on larger servers like what ZFS is targeted for, filesystem performance in all facets is very important.