macOS Tahoe Brings a New Disk Image Format (eclecticlight.co) 25
Apple's macOS 26 "Tahoe" introduces a new disk image format called ASIF, designed to dramatically improve performance over previous formats like UDRW and sparse bundles -- achieving near-native read/write speeds for virtual machines and general disk image use. The Eclectic Light Company reports: 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 C-Command's DropDMG. I'm sure it will support ASIF disk images soon.
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 C-Command's DropDMG. I'm sure it will support ASIF disk images soon.
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
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Asif anyone in their right mind would use a format with that acronym.
You think your data is in that disk image? As If!
But seriously, I'll think about trusting it in three OS releases. I remember all the problems with sparse bundles and Time Machine, so that's not an "I'll trust it in three releases," but rather an "I'll start experimenting with it in three releases."
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:Near native performance? (Score:4, Informative)
Don't most disk formats have basically just native performance? What can you do wrong to degrade the performance?
As can be seen in this table [eclecticlight.co] (from the FA), ASIF is considerably faster than the current UDRW.
Re: Near native performance? (Score:2)
I read the GP question as how did apple fuck this up in the first place?
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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.
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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?
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We are talking about disk images.
Not file systems for hard disks.
So, no idea why you think Apple fucked up, when they invent a faster disk image?
If you run a random virtual machine, you have a big file on the real OS, representing your filesystem in the guest OS. In general, that is a virtual block device with what ever file system your guest OS puts on it.
However disk images are also used as mountable files on Mac OS. It is just a file, that pops up as a (read only) drive in the file system.
So if you think
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So, no idea why you think Apple fucked up, when they invent a faster disk image?
I want to know how they fucked up with the first disk image. That's why you have no idea why I would want to know something I didn't want to know.
So if you think something was fucked up before, perhaps point out what it was?
It was obvious to everyone else. This is a you problem.
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Thin = roughly the size of the data or at least the data marked blocks.
Thick = roughly the full size of the disk volume (sometimes they are compressed or sometimes they are a bit larger than "full size.)
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I could understand why a growing qcow (especially with snapshots) may fragment and cause issues, but a usual disk image without doing anything fancy should be more or less map access to positions in the image file, which I think may only be slowed down if the file itself lies on a complex FS (e.g. with copy-on-write mechanisms)
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Having blocks in linked lists.
Having catalogs/directories on one corner of the hard drive (in tis case, image) and the data on the other.
Having inodes, or having no inodes.
Having meta information like who owns the file/director and access rights in a meta database instead of in the directory or at an inode.
And ... ... ...
So
On
Modern file systems try to estimate how big your file will be, and allocate it as one big chunk. That is one reason why "data recovery" on windows is so easy. You save a file (even if i
didn't we JUST switch file systems recently? (Score:1)
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
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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.
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Ublock origin not working again? Haven't noticed that here. Html-load
Com malware is completely blocked.
Re: didn't we JUST switch file systems recently? (Score:2)
Eight years and hundreds of millions or more devices running it? What are you looking for?
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I think that is a Chrome thing. /. more obnoxious?
But perhaps it is on
Does the format grow/shrink? (Score:2)
With sparse files, if I add a megabyte of data to it, then delete it, and run a TRIM, the sparse file will grow by that and stay at this. Does this new image format actually release space when the image has fewer files and a TRIM command is issued?
Another question is ACID compliance. Are all writes transactional, or if something crashes something screws up the format, so all data on the image is scrozzled? There is a reason why image formats tend to be relatively rare, as they have to be as reliable as f
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As for the ACID compliance of the image- that comes down to whether or not whatever is using the image passes fsync() through.
This doesn't really have anything to do with the image itself. You're concerned about what's running *on* the image, and what the image is stored on.
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If your file does not get smaller after trim, then obviously the filesystem does not support sparse files. Or the file is not marked as sparse ... or you got an error and you failed to read it.
As we are talking about Apple, which never did anything right, obviously if the power fails while you write to a disk image, not only the disk image gets corrupted, but also the main file system on the hard drive.
Worse, when you switch the Mac back on, the power surge will kill your freezer.
Now hurry, and drink the be
Just as if there's a joke in here... (Score:2)
Just as if there's a joke in here, how is this better than QCOW2?