macOS Tahoe Brings a New Disk Image Format (eclecticlight.co)
- Reference: 0178041771
- News link: https://hardware.slashdot.org/story/25/06/13/2021236/macos-tahoe-brings-a-new-disk-image-format
- Source link: https://eclecticlight.co/2025/06/12/macos-tahoe-brings-a-new-disk-image-format/
> Apple provides few technical details, other than stating that the intrinsic structure of ASIF disk images doesn't depend on the host file system's capabilities, and their size on the host depends on the size of the data stored in the disk. In other words, they're a sparse file in APFS, and are flagged as such. [...]
>
> Conclusions:
> - Where possible, in macOS 26 Tahoe in particular, VMs should use ASIF disk images rather than RAW/UDRW.
> - Unless a sparse bundle is required (for example when it's hosted on a different file system such as that in a NAS), ASIF should be first choice for general purpose disk images in Tahoe.
> - It would be preferable for virtualizers to be able to call a proper API rather than a command tool.
> - Keep an eye on [3]C-Command's DropDMG . I'm sure it will support ASIF disk images soon.
[1] https://developer.apple.com/documentation/virtualization/vzdiskimagestoragedeviceattachment/
[2] https://eclecticlight.co/2025/06/12/macos-tahoe-brings-a-new-disk-image-format/
[3] https://c-command.com/dropdmg/
Near native performance? (Score:2)
Don't most disk formats have basically just native performance? What can you do wrong to degrade the performance?
Re: (Score:2)
> Don't most disk formats have basically just native performance? What can you do wrong to degrade the performance?
As can be seen in [1]this table [eclecticlight.co] (from the FA), ASIF is considerably faster than the current UDRW.
[1] https://eclecticlight.co/wp-content/uploads/2025/06/diskimages25.png
Re: Near native performance? (Score:2)
I read the GP question as how did apple fuck this up in the first place?
Re: (Score:2)
I haven't even had a mac in decade+ now, but from my vague recollections MacOS images are generally come with their own file systems. (I've tried to recall an image format for MacOS that is a plain dumb block device - and couldn't. There is no /dev/loop on macs.)
And from this follows: there is a ton of ways one could fuck up performance with a shoddily implemented custom file system for a particular disk image format.
Re: (Score:2)
> And from this follows: there is a ton of ways one could fuck up performance with a shoddily implemented custom file system for a particular disk image format.
I only know a little bit about filesystems (I haven't dug into any deeply since using fsdb on SCO Unix) but even I know that. I want to know, in what particular way did Apple fuck up?
didn't we JUST switch file systems recently? (Score:2)
so now we're going to go through that again? I know, change can be good, but sometimes Apple just seems to want to change things "just because they can".
I just don't think APFS has had enough time to "stew" in the field to get a proper large list of changes and enhancements to make for it yet. They need to sit on this a few more years before making us all reformat our drives again. I want more "bang for the buck" when it comes to inconveniencing me.
Also totally OT, slashdot scrolling my window up and dow
Re: (Score:2)
> so now we're going to go through that again?
No. The article is about a replacement for dmg files, not the format used on the HD.
Re: (Score:2)
Ublock origin not working again? Haven't noticed that here. Html-load
Com malware is completely blocked.
What an incredibly bad name. (Score:5, Funny)
Asif anyone in their right mind would use a format with that acronym.
Re:What an incredibly bad name. (Score:4, Funny)
Don't have a qcow, man.
Re: What an incredibly bad name. (Score:2)
Nice thanks for sharing. /sarcasm