4 ms·

Without encryption, compression, or deduplication on I don't think there would be very much overheard - more than traditional file systems, definitely, but stil

Without encryption, compression, or deduplication on I don't think there would be very much overheard - more than traditional file systems, definitely, but still relatively very little. Encryption would require significantly more CPU (http://forums.freebsd.org/showthread.php?t=9886 http://forums.freebsd.org/showthread.php?t=9886) Compression would require moderately more CPU (depends heavily on the compression algorithm) though you can actually speed up disk access with this - which is the real bottleneck (http://blogs.sun.com/observatory/entry/zfs_compression_a_win_win http://blogs.sun.com/observatory/entry/zfs_compression_a_win...) Deduplication requires lots of memory (I think I saw 1-2GB per TB of data quoted someplace) and will increase CPU load a bit, but for certain workloads can save a lot of writing and diskspace (think Virtual Images or a dataset like Dropbox's). I'm not involved in ZFS development (just an avid user) so take this with a grain of salt.

newman314 16y ago
With new Core iX processers now being able to do AES in hardware, I wonder if the CPU requirement for encryption will go down significantly once/if support is enabled.
- ciupicri 16y ago
  Not all Core iX processors have support for the new AES instructions.
  - newman314 16y ago
    From what I can tell, most if not all of the new Sandy Bridge based Core iX processors will.
zdw 16y ago
ZFS lets you put encryption/compression/dedupe on a per filesystem basis, and filesystems are extremely light and easy to create in ZFS (one/multiple per home directory or installed app is normal) so it's easy enough to only apply those features where they're needed. As ZFS checksums every block in the CPU anyway, doing an additional crypto step isn't all that bad, especially in a server environment where there cores are plentiful.
codex 16y ago
ZFS will also verify the checksum of each data block, which means that by default it is not a zero-copy filesystem. sendfile(), recvfile(), etc. will all require at least one read pass. This isn't necessarily a bad thing--in my experience, ZFS has caught on-disk bit rot several times. However, it may not be worth it on an iPhone or other low-power device. Fortunately, it can be disabled.

newman314 16y ago

With new Core iX processers now being able to do AES in hardware, I wonder if the CPU requirement for encryption will go down significantly once/if support is enabled.

ciupicri 16y ago
Not all Core iX processors have support for the new AES instructions.
- newman314 16y ago
  From what I can tell, most if not all of the new Sandy Bridge based Core iX processors will.

zdw 16y ago

ZFS lets you put encryption/compression/dedupe on a per filesystem basis, and filesystems are extremely light and easy to create in ZFS (one/multiple per home directory or installed app is normal) so it's easy enough to only apply those features where they're needed. As ZFS checksums every block in the CPU anyway, doing an additional crypto step isn't all that bad, especially in a server environment where there cores are plentiful.

codex 16y ago

ZFS will also verify the checksum of each data block, which means that by default it is not a zero-copy filesystem. sendfile(), recvfile(), etc. will all require at least one read pass. This isn't necessarily a bad thing--in my experience, ZFS has caught on-disk bit rot several times. However, it may not be worth it on an iPhone or other low-power device. Fortunately, it can be disabled.