Apple's newly launched ASIF disk format claims to allow virtual disks to run at nearly the native speed of solid-state drives. This is a real performance breakthrough for users who often use disk images and virtual machines.
Technology upgrade solves speed bottleneck
In the past, when using disk images on Mac, especially when using encrypted formats, transfer speed was often a frustrating issue. Even with the latest M-series chips and high-speed SSDs, the read and write speeds of traditional images are often limited to less than 100 megabytes per second, which has a serious impact on work efficiency.
The new ASIF format changes this situation from the bottom up. It does not rely on the function of the host file system when transmitting data. Its internal structure has been specially optimized. This design makes the movement path of data between the host and the disk more direct, reducing the losses caused by intermediate links, thus laying the foundation for a leap in speed. This design makes the movement path of data between the host and the disk more direct, reducing the losses caused by intermediate links, thus laying the foundation for a leap in speed.
The measured performance is close to that of a physical hard disk
During testing at WWDC 2025, the performance data of the new format was impressive. On a MacBook Pro equipped with an M3 Pro chip, read and write operations were performed on an ASIF image with a capacity of 100GB, and the speeds reached 5.8GB and 6.6GB per second respectively.
Even if encryption protection measures are enabled, the read and write speeds are still at a high level of 4.8GB and 4.6GB per second. More powerful hardware can unleash its greater potential. On the Mac mini equipped with M4 Pro, writing speeds exceeding 8GB per second have even been observed, which is no different from the actual performance of many high-end NVMe solid-state drives.
Sparse characteristics improve storage efficiency
"Apple Sparse Image Format" is the full name of ASIF, which means Apple Sparse Image Format. This format has a "sparse" characteristic. This characteristic indicates that the physical space it occupies in the file system is only proportional to the amount of data actually stored in the image, not the entire pre-allocated image capacity.
For example, if you build an ASIF disk image with a capacity of 1TB and only store a 200GB file, it will only occupy about 200GB of space on the hard disk. This is different from the traditional image pre-filling the entire capacity, which can effectively avoid the waste of storage space and is very friendly for managing large-capacity virtual disks.
Professional tools currently have a high threshold
In the first macOS 26 Tahoe system to support this format, the normal user interface does not provide the option to create or manage ASIF images. Users must currently use the "Disk Utility" program or the terminal command line to operate, which has a certain threshold for non-technical users.
Apple has not made it clear whether it will put that feature into earlier versions of the operating system, nor has it said when other systems will be compatible to read this new format. This means that users of earlier versions of Mac may not be able to enjoy the benefits of this technology for the time being, and file sharing may also be restricted.
Virtualization applications benefit significantly
For virtual machine users, this advancement plays a critical role. The virtual machine core file is actually a special disk image, and its read and write speed will directly have a decisive impact on the smooth running of the virtual system. The performance improvements brought by ASIF can enable macOS or Windows virtual machines to achieve a response speed that is close to that of running on a physical machine.
For developers, this means more efficient translation, for testers, it means a faster software testing cycle, and for users who need to work across platforms, it means a smoother multi-system switching experience, which can significantly save time and costs.
Future development and compatibility expectations
Although ASIF has significant advantages in terms of performance, it will take time for its ecosystem to mature. In addition to the creation threshold, its cross-platform compatibility is also a major concern. If the format is only limited to the latest macOS, it will limit its application in team collaboration or data exchange scenarios.
The industry is focused on the possibility of Apple opening up the relevant specifications to developers or promoting them to evolve into a more universal industry standard. In addition, when third-party virtualization software, such as Parallels Desktop and VMware Fusion, can adapt and use this new format, this will also have an impact on its popularity rate.
Is it possible that for those users who are in certain professional fields and need to process large-scale files very tediously and frequently in their daily work, or run virtual machines, will the emergence of the ASIF format be influential enough to drive you to upgrade to macOS 26 at a faster speed? Welcome to the comment area and share your personal views. If you personally feel that this article is helpful, please support it by giving it a like.
