3 ms·

True, but how many modern file system solutions provide snapshots for all users. Fossil and Venti will do that for you.

by rbc 12y ago

ChuckMcM 12y ago
WAFL (netapp) and ZFS (sun) to name two?
- 4ad 12y ago
  I think the poster was trying to say that this article is interesting despite its age, because versioned file systems are still a rare bunch. I would love to use ZFS everywhere, but sadly I use it almost nowhere. I think that was also parent's point. Other than that, even considering snapshotted filesystems, I still think venti model is worth discussing because the model is just so different. No deletion, and it doesn't expose a filesystem-like layer. It exposes a much simpler and deeper abstraction.
  - ChuckMcM 12y ago
    Interesting data point, since nearly all of my computer use is constrained to be in and around home, I use ZFS and WAFL pretty much everywhere, between the filer that I've built and the one I bought. All 'changable' data lives on them so that a system failure can be quickly recovered from. It makes a windows laptop with a small Flash drive a lot more tolerable in my experience. If you could make it possible to use ZFS in one place that you cannot use it today, what would that place be?
    - 4ad 12y ago
      The number one reason I don't use ZFS is that I have to use Linux and OS X. My data at home indeed does reside on ZFS, and I also have a few Solaris machines in the cloud, but a huge part of what I have to do, I have to do on Linux. This is not my decision, and usually I can't influence it. ZFS does run on Linux, but it's not by default, so from the perspective of the people I have to work with, it could as well not exist. But you asked me only about a single place; my OS X laptop. After I use Solaris for a while (where I have automatic snapshots), when I come back to OS X I feel so weird that I have to remember that I can't just delete a file and recover it from a snapshot. Also, I've experienced silent data corruption on my laptops; this would be detected by ZFS (unfortunately it wouldn't be solved, as laptops with more than one hard drive are very rare, but with mSATA and a SSD, now there's at least a way on some laptops). I also have to run old versions of Go every day; on Solaris I have versions of binaries from every commit and I can just run them to test something. On OS X is more complicated, I use venti, but since it's not integrated with the filesystem (because FUSE sucks), as on Plan 9, it's more annoying.
cmurf 12y ago
ZFS, Btrfs do this with COW. NTFS (volume snapshot service) and ReFS makes it COW. LVM2 offers a new thinp COW based snapshot that could make this work for any filesystem. Edit: And Apple's CoreStorage also has some kind of COW capability at least when used for "fusion" drives. And then Time Machine and OSTree are effectively COW as well. The trick here is how to make what's written, read-only and thus write once. Btrfs at least has the concept of read-only seed devices, which can be put together in sequence, but might need some work to make it fit better with this use case.
- cmurf 12y ago
  If delaying the "write once" aspect of a volume (or tree) is OK, several of the above options offer read-only snapshots. Btrfs ro snapshots aren't writable even by root. They can be deleted or a rw snapshot can be made from them.
- enneff 12y ago
  IIUC both ZFS and btrfs require that you be root to work with file system snapshots.
  - cmurf 12y ago
    On Btrfs an unprivileged user can create subvolumes/snapshots. There's a mount option that lets them remove subvolumes they own.
    - enneff 12y ago
      I didn't know that. Very cool!
  - 4ad 12y ago
    Solaris has a fine-grained privilege model where you can delegate any aspect of any dataset to any user. However, FreeBSD and Linux don't have this, so on those systems you have to be root to do snapshots.
    - 12y ago

True, but how many modern file system solutions provide snapshots for all users. Fossil and Venti will do that for you.

by rbc 12y ago

True, but how many modern file system solutions provide snapshots for all users. Fossil and Venti will do that for you.

ChuckMcM 12y ago

WAFL (netapp) and ZFS (sun) to name two?

4ad 12y ago
I think the poster was trying to say that this article is interesting despite its age, because versioned file systems are still a rare bunch. I would love to use ZFS everywhere, but sadly I use it almost nowhere. I think that was also parent's point. Other than that, even considering snapshotted filesystems, I still think venti model is worth discussing because the model is just so different. No deletion, and it doesn't expose a filesystem-like layer. It exposes a much simpler and deeper abstraction.
- ChuckMcM 12y ago
  Interesting data point, since nearly all of my computer use is constrained to be in and around home, I use ZFS and WAFL pretty much everywhere, between the filer that I've built and the one I bought. All 'changable' data lives on them so that a system failure can be quickly recovered from. It makes a windows laptop with a small Flash drive a lot more tolerable in my experience. If you could make it possible to use ZFS in one place that you cannot use it today, what would that place be?
  - 4ad 12y ago
    The number one reason I don't use ZFS is that I have to use Linux and OS X. My data at home indeed does reside on ZFS, and I also have a few Solaris machines in the cloud, but a huge part of what I have to do, I have to do on Linux. This is not my decision, and usually I can't influence it. ZFS does run on Linux, but it's not by default, so from the perspective of the people I have to work with, it could as well not exist. But you asked me only about a single place; my OS X laptop. After I use Solaris for a while (where I have automatic snapshots), when I come back to OS X I feel so weird that I have to remember that I can't just delete a file and recover it from a snapshot. Also, I've experienced silent data corruption on my laptops; this would be detected by ZFS (unfortunately it wouldn't be solved, as laptops with more than one hard drive are very rare, but with mSATA and a SSD, now there's at least a way on some laptops). I also have to run old versions of Go every day; on Solaris I have versions of binaries from every commit and I can just run them to test something. On OS X is more complicated, I use venti, but since it's not integrated with the filesystem (because FUSE sucks), as on Plan 9, it's more annoying.

cmurf 12y ago

ZFS, Btrfs do this with COW. NTFS (volume snapshot service) and ReFS makes it COW. LVM2 offers a new thinp COW based snapshot that could make this work for any filesystem. Edit: And Apple's CoreStorage also has some kind of COW capability at least when used for "fusion" drives. And then Time Machine and OSTree are effectively COW as well. The trick here is how to make what's written, read-only and thus write once. Btrfs at least has the concept of read-only seed devices, which can be put together in sequence, but might need some work to make it fit better with this use case.

cmurf 12y ago
If delaying the "write once" aspect of a volume (or tree) is OK, several of the above options offer read-only snapshots. Btrfs ro snapshots aren't writable even by root. They can be deleted or a rw snapshot can be made from them.
enneff 12y ago
IIUC both ZFS and btrfs require that you be root to work with file system snapshots.
- cmurf 12y ago
  On Btrfs an unprivileged user can create subvolumes/snapshots. There's a mount option that lets them remove subvolumes they own.
  - enneff 12y ago
    I didn't know that. Very cool!
- 4ad 12y ago
  Solaris has a fine-grained privilege model where you can delegate any aspect of any dataset to any user. However, FreeBSD and Linux don't have this, so on those systems you have to be root to do snapshots.
  - 12y ago