Jag rekommenderar verkligen en läsning av The loss of ZFS som jag länkade tidigare. Där tas t.ex. BtrFS upp och varför det är bättre än ZFS. Och även vilka nackdelar som ZFS medför för Apples ändamål.
Angående diskussionen om ZFS som plattformsoberoende filsystemet och varför det ändå inte skulle bli det eftersom ZFS inte är lämpligt som ett generellt gränssnitt för att flytta data:
There are complicated features you want for your boot drives and system disks. Ideally you could have them on your interchange disks, but there are other features that are more important, particularly interoperability, and simplicity. ZFS didn't bring either of those. There might have been a few people who were psyched to be able to use ZFS to share disks between a Mac and a Solaris or FreeBSD box, but honestly those people are few and far between. Whether Apple used ZFS or something else it is just as interoperable with Linux and Windows (which is to say, not at all). So that fact that Apple looks to be doing a new FS does not impact interoperability in any real sense.
The other feature you really want for an interchange FS is simplicity. There are a lot of devices out there that use an FS to communicate with a computer. The simplest example is a digital camera via its media cards, but there are many others. Something like ZFS is way too complex for those devices, and honestly most of the features of ZFS like multiple drive support and snapshots are useless since the devices don't have the physical interconnects or user interfaces to expose those features. There is certainly an argument to be made that we could use something a bit better than FAT32 or exFAT as that format, but ZFS was not the right solution for that.
In other words, for that disk you want to use as an external drive to drag between computers you don't want something like ZFS, you want something that is simple enough that a firmware engineer can write a read-only implementation from the specs in less than a week. For the disk embedded in your computer (operationally or literally) you want something like ZFS, but it doesn't matter if it is interoperable with anything else because you won't be moving it between systems.
This is basically how Windows works. Microsoft generally uses NTFS for internal drives, but FAT for external drives. Ultimately somebody should design a filesystem explicitly for use as an interchange format and license it for free, then everyone can deal with their internal FSes and do what makes the most sense for their OSes and markets.
Resten av mitt inlägg är mera OT:
Det står även en intressant grej om hur Apple jobbar som jag sett andra ta upp förut: Med väldigt små team. Inom utveckling och programmering gäller i högsta grad att fler kockar inte automatiskt betyder bättre soppa. Jag har läst skräckhistorier från utvecklare som jobbat på Microsoft och vilken mardröm det kan vara att få igenom en liten finess eller buggfix genom lagret av management och arbetsgrupper.
Såhär skriver Louis Gerbarg om Apples team:
This is a particularly acute problem at Apple, which traditionally has done things with very few engineers. I don't want to get into exact numbers, but I recall having a discussion with the head of a university FS team who was discussing the FS he was working on. He was pitching it to a group of Apple engineers. It was some interesting work, but there were some unsolved problems. When he was asked about them he commented that they didn't have enough people to deal with them, but he had some ideas and it shouldn't be an issue for a company with a real FS team. It turned out his research team had about the same number of people working on their FS as Apple had working on HFS, HFS+, UFS, NFS, WebDAV, FAT, and NTFS combined. I think people don't appreciate how productive Apple is on a per-engineer basis.
Det har förstås sina nackdelar också, men på det hela verkar det fungera bra för Apple.
