Inevitably, both grew in size correspondingly. What I then did to my two 50 GB sparse bundles was copy in seven hunky PDFs, totalling a little over 41 MB. Interestingly, DropDMG creates slightly smaller empty sparse bundles than Disk Utility does. For an empty sparse bundle, the overhead imposed by APFS is significantly smaller: just six bands, none of which comes close to the 8.4 MB maximum, while the same empty sparse bundle in HFS+ requires 23 bands, most of which are 8.4 MB. (Thanks to Cyclo Pontivy for telling me that.)Īlthough HFS+ and APFS sparse bundles use the same maximum band size, empty sparse bundles differ substantially in size: for HFS+ this is around 165.3 MB for a sparse bundle which can grow to 50 GB for APFS this is only 24.8 MB. In some special circumstances, for Time Machine backups to networked disks, for example, the band size can rise to 268.4 MB to minimise the number of bands require for large backups. When freshly created, an empty APFS sparse bundle which can grow up to 50 GB in size only occupies around 25 MB, using a band size of up to 8.4 MB. This should make it easier for a sparse bundle’s size to track that of its contents. They differ in how they store their data: sparse disk images are single files, whereas sparse bundles are really folders, within which the data for the disk image is divided into separate files, or bands. The two sparse image formats are small when empty, and grow up to the pre-set maximum as they need. Make an ordinary disk image of 1 GB, and that’s the space (plus a little overhead) that it requires on disk. Sparse bundles are one of two varieties of disk images which have the great advantage that they don’t occupy a fixed size, and can grow and shrink as they need. HFS+ sparse bundles are dependable and can be compacted with DropDMG.” This article looks at how well macOS manages space in sparse bundles in HFS+ and APFS: the short answer is badly. Most importantly, it’s able to compress them.ĭropDMG’s developer Michael Tsai commented to my previous article that “I don’t see much reason to use APFS disk images, except for testing how an app works with APFS. As far as I can see it’s the only utility which does pretty well everything else you might want to do with regular fixed-size disk images and sparse bundles. Although, as I explained just over two weeks ago, there are numerous issues with supporting utilities for APFS-format sparse bundles, they work fine in HFS+, and are even better-supported by C-Command’s wonderful DropDMG.ĭropDMG is primarily aimed at those working with disk images for the delivery of apps, and has extensive features for software licence agreements, custom volume icons, background images, and icon layouts. They can do much more than provide a convenient means to distribute software, particularly when you use their variable-size variety, the sparse bundle. Disk images are one of those wonderful ideas which we take for granted, and can be powerful tools.
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