Hi, I downloaded the latest afsctool and then used it to compress one of my Lion installation partitions. Code: /Volumes/HGST-2.5-7200-PART2/: Number of HFS+ compressed files: 282978 Total number of files: 302274 Total number of folders: 76309 Total number of items (number of files + number of folders): 378583 Folder size (uncompressed; reported size by Mac OS 10.6+ Finder): 13808049564 bytes / 14.6 GB (gigabytes) / 13.6 GiB (gibibytes) Folder size (compressed - decmpfs xattr; reported size by Mac OS 10.0-10.5 Finder): 8720691978 bytes / 8.98 GB (gigabytes) / 8.37 GiB (gibibytes) Folder size (compressed): 8910985079 bytes / 9.17 GB (gigabytes) / 8.54 GiB (gibibytes) Compression savings: 35.5% Approximate total folder size (files + file overhead + folder overhead): 9355235942 bytes / 9.36 GB (gigabytes) / 8.71 GiB (gibibytes) It compressed the partition but afterwards the partition was no longer bootable. It now showed up in the list of bootable partitions as EFI Boot instead of its regular name. So I decompressed the partition using afsctool and it again become bootable and its regular name showed up in the list of bootable partitions. So then I just tried compressing the System/ directory and once again the partition became unbootable. So apparently there is something that should not be compressed under System/ directory when using afsctool. Does anyone have any ideas about how to successfully compress an entire partition that will remain bootable using afsctool? .