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Apple HFS+ didn't have file data checksums either. The default filesystem on most Linux distributions, ext4 doesn't, it just stores checksums of the file metada
by jchb 9y ago
Apple HFS+ didn't have file data checksums either. The default filesystem on most Linux distributions, ext4 doesn't, it just stores checksums of the file metadata, not the file data. Same story with Windows NTFS filesystem. Microsofts newer ReFS filesystem has file data checksums disabled by default.
So it seems like a tradeoff that most of the major operating system are making. Most likely related to performance.
Edit: macOS disk images do have a checksum of the whole image data though. The issue mentioned in the article seems to be caused by an oversight in the disk image helper app, rather than in the APFS filesystem itself.
- temprature 9y agoPerformance is only an issue if your disk can write faster than your CPU can hash. hammer2 changed its hash a couple of years ago because this started happening with newer NVMe drives[0], but before that disk writes weren't CPU-bound. [0] http://lists.dragonflybsd.org/pipermail/commits/2016-June/500610.html http://lists.dragonflybsd.org/pipermail/commits/2016-June/50...
- jchb 9y agoWhat about: * Disk reads may unnecessarily trash the CPU caches, because CPU will need to verify the checksum when the DMA read is done, even if the app isn't going to process the data immediately afterwards * Battery life - without checksums the CPU can stay mostly idle, and go into a lower power mode, while the disk controller does its job