Storage and file systems, HFS and legacy, kSKDiskRoleLegacyMacData and kSKDiskTypeHFS

[grahamperrin]

Spun off from https://forums.macrumors.com/showthread.php?p=20116744&legacy#post20116744

Curious. In logs for pre-release and released builds of OS X 10.10 Yosemite, this (for example):

… OSInstaller[402]: Evaluating SKDisk { BSD Name: disk2s2 Mount point: / Role: kSKDiskRoleLegacyMacData Type: kSKDiskTypeHFS }

If this is an indication that the HFS Plus file system is already, in some way, a legacy aspect of developments by Apple: I should not assume that what's to follow will be limited to Mac hardware. But if Macs begin to use something other than HFS Plus by default, I don't expect iOS to make the same transition at the same time.

 

[wrldwzrd89]

Spun off from https://forums.macrumors.com/showthread.php?p=20116744&legacy#post20116744

Curious. In logs for pre-release and released builds of OS X 10.10 Yosemite, this (for example):

… OSInstaller[402]: Evaluating SKDisk { BSD Name: disk2s2 Mount point: / Role: kSKDiskRoleLegacyMacData Type: kSKDiskTypeHFS }

If this is an indication that the HFS Plus file system is already, in some way, a legacy aspect of developments by Apple: I should not assume that what's to follow will be limited to Mac hardware. But if Macs begin to use something other than HFS Plus by default, I don't expect iOS to make the same transition at the same time.

I noticed this myself, and I think you are on to something. My guess is btrfs.

 

[MikhailT]

I noticed this myself, and I think you are on to something. My guess is btrfs.

Not going to happen, BTRFS is under GPL. Apple refuses to accept GPL.

Apple will build their own FS from scratch that'll take the best features from ZFS/BTRFS IMO.

 

[Mr. Retrofire]

From
http://en.wikipedia.org/wiki/Hierarchical_File_System#History

“In 1998, Apple introduced HFS Plus to address inefficient allocation of disk space in HFS and to add other improvements. HFS is still supported by current versions of Mac OS, but starting with OS X, an HFS volume cannot be used for booting, and beginning with OS X 10.6 (Snow Leopard), HFS volumes are read-only and cannot be created or updated.”

HFS is deprecated, not HFS+ and HFS+J.

 

[grahamperrin]

kSKDiskRoleLegacyMacData for all four types of HFS Plus, I guess

… HFS is deprecated, not HFS+ and HFS+J.

The type for HFS+J is kSKDiskTypeHFS – a somewhat generic 'HFS' at the tail of that string.

Without testing, it's reasonable to assume that all four types of HFS Plus are, for (at least) the purpose of installing OS X Yosemite:

• type kSKDiskTypeHFS
• role kSKDiskRoleLegacyMacData

– that's legacy, not deprecated.

(We should not expect Yosemite to install to a slice where HFS Plus is not journaled, but that's a separate topic.)

Types of HFS Plus

Quote:

… Apple's hdiutil(1) Mac OS X Manual Page lists four HFS filesystem types for creation purposes:

• HFS+
• HFS+J (JHFS+)
• HFSX
• JHFS+X

The less commonly used expression JHFSX is probably an informal abbreviation of JHFS+X.​

– In the disk of an iPhone, are both HFSX slices journaled?​

 

[sjinsjca]

Spun off from https://forums.macrumors.com/showthread.php?p=20116744&legacy#post20116744

Thanks for this.

Since Lion, the file system has been gradually and steadily abstracted in both OS X and iOS. There has to be a reason. Looking at the ancient HFS family tree while comparing to the more modern file systems like BTRFS, ZFS and ReiserFS, OS X's file system looks positively dusty.

Then there's the cloud. Fresh thinking is needed beyond the Dropbox model.

Ergo, something is due. Apple isn't doing the abstraction just to keep its engineers busy.

 

[2984839]

Apple would do well to look at DragonflyBSD's HAMMER and HAMMER2 filesystems. I think they would be a very good fit for what Apple is trying to accomplish and they wouldn't have any licensing issues, since the code is under the DragonflyBSD license, not the GPL.

Here's an example of some stuff you can do with HAMMER: http://www.dragonflybsd.org/docs/docs/howtos/howtorecoverdataonhammerfs/