7 ms·

Maybe Oracle is less willing than Sun to license their core differentiating server feature to competitors. I believe Time Machine is still built on top of ZFS

by mustpax 17y ago

Maybe Oracle is less willing than Sun to license their core differentiating server feature to competitors. I believe Time Machine is still built on top of ZFS snapshot though. So obviously some ZFS code remains. Edit: Apparently Time Machine is not based on ZFS. So it seems ZFS is completely off the map after all.

Locke1689 17y ago
Actually,Time machine is not and has never been based on zfs. It is implemented using hfs+, journaling, and a kernel/fs modification for journaling and hard links. A time machine snapshot is basically modified hard link journals.
- Herring 17y ago
  You clearly have a solid backup infrastructure.
  - Locke1689 17y ago
    By that I mean that it saves hard links to "bundles" which haven't changed. P.S. Woops, iPhone + airport == spotty internet.
Locke1689 17y ago
Actually,Time machine is not and has never been based on zfs. It is implemented using hfs+, journaling, and a kernel/fs modification for journaling and hard links. A time machine snapshot is basically modified hard link journals.
- rbanffy 17y ago
  The sad part is that Time Machine would be a one-liner had OSX supported ZFS since Leopard...
  - glhaynes 17y ago
    Which one line (heck, doesn't have to just be one) command would you issue to get Time Machine-like functionality from ZFS? ZFS contains a lot of features that sound like they overlap with Time Machine, but in practice they really don't in a way that would make Time Machine a "free" feature.
    - furyg3 17y ago
      I implemented a simple personal backup solution a long time ago which is (essentially) what Time Machine implements now (without the eye-candy application, of course). It's not that hard, it only requires hard-linking, which the OS X kernel didn't support, so they added it. Steps: First run: * Rsync data from source drive to backup drive (can be done over network, ssh, whatever). We'll call this backup "0" Second run: * On the backup drive, copy the last backup folder (backup "0") to a new backup folder (backup "1"), using hardlinks. Hardlink copies don't take any additional space, since they're pointing to the original resource on the disk (folders do add some negligible space). * Rsync data from source drive to backup drive (backup "1"). Rsync, of course, only updates what's new/changed. Repeat, saving as far back as you'd like, and deleting old backups if the drive is full, after N backups, or so many days. Now you've got an easy incremental backup bash script. Hardlinks are beautiful, because they don't add extra space, and once all the hardlinks to a resource are deleted the resource becomes free space. This isn't an enterprise-level backup solution, but it's a great quick-and-dirty way to do incremental backups, and is exactly how Time Machine works.
      - vsync 17y ago
        rsnapshot works exactly that way as well and is a supported package.
      - glhaynes 17y ago
        One way this isn't exactly like Time Machine: since it doesn't hook into the FSEvents journal of file system modifications, rsync has to check the modified dates of every file in the backup set. With FSEvents, Time Machine knows what's changed (or at least which folders contain changed items) and can deal with only those. But, yeah, same basic concept for sure.
wmf 17y ago
Apple dropped ZFS from Snow Leopard before Oracle bought Sun (and the acquisition hasn't even closed yet; AFAIK companies are supposed to behave as if nothing is going to happen until the deal closes).

by mustpax 17y ago

Locke1689 17y ago

Actually,Time machine is not and has never been based on zfs. It is implemented using hfs+, journaling, and a kernel/fs modification for journaling and hard links. A time machine snapshot is basically modified hard link journals.

Herring 17y ago
You clearly have a solid backup infrastructure.
- Locke1689 17y ago
  By that I mean that it saves hard links to "bundles" which haven't changed. P.S. Woops, iPhone + airport == spotty internet.

Locke1689 17y ago

rbanffy 17y ago
The sad part is that Time Machine would be a one-liner had OSX supported ZFS since Leopard...
- glhaynes 17y ago
  Which one line (heck, doesn't have to just be one) command would you issue to get Time Machine-like functionality from ZFS? ZFS contains a lot of features that sound like they overlap with Time Machine, but in practice they really don't in a way that would make Time Machine a "free" feature.
  - furyg3 17y ago
    I implemented a simple personal backup solution a long time ago which is (essentially) what Time Machine implements now (without the eye-candy application, of course). It's not that hard, it only requires hard-linking, which the OS X kernel didn't support, so they added it. Steps: First run: * Rsync data from source drive to backup drive (can be done over network, ssh, whatever). We'll call this backup "0" Second run: * On the backup drive, copy the last backup folder (backup "0") to a new backup folder (backup "1"), using hardlinks. Hardlink copies don't take any additional space, since they're pointing to the original resource on the disk (folders do add some negligible space). * Rsync data from source drive to backup drive (backup "1"). Rsync, of course, only updates what's new/changed. Repeat, saving as far back as you'd like, and deleting old backups if the drive is full, after N backups, or so many days. Now you've got an easy incremental backup bash script. Hardlinks are beautiful, because they don't add extra space, and once all the hardlinks to a resource are deleted the resource becomes free space. This isn't an enterprise-level backup solution, but it's a great quick-and-dirty way to do incremental backups, and is exactly how Time Machine works.
    - vsync 17y ago
      rsnapshot works exactly that way as well and is a supported package.
    - glhaynes 17y ago
      One way this isn't exactly like Time Machine: since it doesn't hook into the FSEvents journal of file system modifications, rsync has to check the modified dates of every file in the backup set. With FSEvents, Time Machine knows what's changed (or at least which folders contain changed items) and can deal with only those. But, yeah, same basic concept for sure.

wmf 17y ago

Apple dropped ZFS from Snow Leopard before Oracle bought Sun (and the acquisition hasn't even closed yet; AFAIK companies are supposed to behave as if nothing is going to happen until the deal closes).