![]() ![]() ![]() ![]() However, attempting to reduce the size of the existing container to anything less than about 18 MB results in failure in Disk Utility because the intended size is considered too small for an empty container. What isn’t perhaps immediately obvious here is that these limits apply to the existing container, not any newly-created container. Maximum (constrained by partition map space): 100.0 MB (99983360 Bytes) Recommended minimum (if used with macOS): 100.0 MB (99983360 Bytes) Minimum (constrained by file/snapshot usage): 4.2 MB (4194304 Bytes) Resize limits for APFS Physical Store partition disk7s1:Ĭurrent Physical Store partition size on map: 100.0 MB (99983360 Bytes) For example, when used on the single default container on an APFS disk image of 100 MB, it returns Where is the name of an APFS Physical Store partition such as disk7s1, returns four limits for the container size on any disk. The commandĭiskutil resizeContainer limits The command tool diskutil advises different limits. Which creates one of only 1.1 MB quite happily, with a container of only 1.1 MB, and a single volume of 1.1 MB too. Hdiutil create -size 1.1m -fs APFS test2.dmg It’s possible to create smaller APFS disk images in Terminal, using a command such as the smallest volume size is 8.4 MB when there’s only one container and one volume, 20 MB when there are two or more containers, or about 300 MB when there are two or more volumes in the same container.the smallest container size is 8.4 MB when there’s only one container, but around 20 MB when there are two or more.This results in the anomalous situation that: two containers, each with only one volume.one container, one volume, to which you could then add either a second container or a second volume, but not both.However, once you’ve created multiple volumes in a single container, you’ll be unable to increase the number of containers if the result would break the rule for the maximum number of volumes.įor example, if you create a disk image of 600 MB, the rules allow you to configure it in any of the following ways: The smallest container which supports more than one volume is just under 600 MB, which is consistent with the formula given in the documentation. If you want two or more containers on a disk image, then you must create an image which is 40 MB or larger in the first place, which still only supports a single volume in each container. Given the information above from the APFS documentation, you might be tempted to try a minimum disk image size of 1.1 MB, but if you enter any size below 8.4 MB, Disk Utility emits a system beep and creates its smallest disk image of 8.4 MB, with a single container of 8.4 MB, and one volume of the same size. When you create a simple read-write disk image, you choose its total size, and that determines its default single container size, which in turn determines how many volumes it can support. For a container this size, statically allocated metadata takes up about a third of the available space.”Īdditionally, the maximum length of an APFS volume name is 256 characters (I presume UTF-8), something I’ll not discuss further here. This value is slightly less that the capacity of a floppy disk. #define NX_MINIMUM_CONTAINER_SIZE 1048576 The smallest supported size, in bytes, for a container. The documentation gives two other limits which are of importance: the minimum size of a container is 1.048576 MB (1048576 bytes), which would therefore be able to contain just a single volume: So if your container is 1.1 GiB in size, the maximum number of volumes it can support is not 100, but only 3. However, there’s a smaller limit which is more likely to come into play: in any given container, the maximum number of volumes is the size of that container divided by 512 MiB, rounded up to the nearest integer. The absolute maximum is 100, which is hardly likely to be reached unless you’re doing very peculiar things. This article explains where ordinary users can run into trouble with APFS containers and volumes, on both physical disks and in disk images.īecause APFS is rather more complex than HFS+ in the way that it handles space on disks, I remind you that each disk is divided into one or more APFS containers which don’t share space, then within each container there are one or more volumes which share the space within their container.ĪPFS limits the number of volumes which can exist within each container. And in the version of Disk Utility shipped with Mojave, they’re even easier to hit. However, buried away in those pages are some which you could readily reach. Reading Apple’s APFS documentation, you’d think it would be very hard for any user to reach its limits. ![]()
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