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I agree that it's a strange set of choices. Eliminating quotas and compression might be OK for something positioned as a basic filesystem, but for something bi

I agree that it's a strange set of choices. Eliminating quotas and compression might be OK for something positioned as a basic filesystem, but for something billed as a "next generation" filesystem it seems odd. Eliminating extended attributes is an even bigger step backward, because they're such a useful building block for other OS features (e.g. look at their use to in Linux to support ACLs and security labels). Failing to support sparse files, though . . . man, that's just insane. That would relegate ReFS to the status of a toy in most filesystem developers' minds, even before you consider their increasing usefulness when storing virtual-machine disk images in a shared filesystem to support migration, etc. It's hard to imagine that none of the many people who must be involved in this at MS raised the red flag. What seems more likely, from what I know of MS culture, is that some people did raise it but then some idiot dictator with a reputation built on some long-irrelevant project ignored or dismissed their objections.

mappu 15y ago
I'm pretty sure Microsoft's VHD file format has built-in support for sparse volumes... maybe it was a case of since they didn't need it, they could trim everyone else's advantage. Since ReFS doesn't look to be in the client version of Windows 8, though, i don't think it'll make much difference to applications - and i expect they'll add some of these features back before Windows 9. Hopefully they have a more transparent versioning system than NTFS this time around
sfoskett 15y ago
If ReFS is really in the Server version of 8, and if it really doesn't support sparse files, consider the implication of built-in deduplication. It does sparse files at a layer above the filesystem, along with dedupe and compression. Or, as mappu points out, ReFS could assume it's running on VHD/CSV, punting those features to a lower level. Perhaps Microsoft is making a decision to focus the filesystem on being a simple storage engine and moving features into other modules (primarily) above or even below it?
- CPlatypus 15y ago
  Dedup isn't quite the same as sparse files. If the filesystem is unaware of dedup, then it still has to allocate its own structures corresponding to the dedup'ed space, seeking to the next hole or next allocated block won't work (not that many applications are smart about holes or that MS didn't already suck in that area), etc. Dedup - even in its most absolutely simple form of just detecting zero blocks - does at least avoid the fatal problem of allocating actual disk space uselessly, but sparse files are still basically a filesystem problem and need to be treated as such.

mappu 15y ago

I'm pretty sure Microsoft's VHD file format has built-in support for sparse volumes... maybe it was a case of since they didn't need it, they could trim everyone else's advantage. Since ReFS doesn't look to be in the client version of Windows 8, though, i don't think it'll make much difference to applications - and i expect they'll add some of these features back before Windows 9. Hopefully they have a more transparent versioning system than NTFS this time around

sfoskett 15y ago

If ReFS is really in the Server version of 8, and if it really doesn't support sparse files, consider the implication of built-in deduplication. It does sparse files at a layer above the filesystem, along with dedupe and compression. Or, as mappu points out, ReFS could assume it's running on VHD/CSV, punting those features to a lower level. Perhaps Microsoft is making a decision to focus the filesystem on being a simple storage engine and moving features into other modules (primarily) above or even below it?

CPlatypus 15y ago
Dedup isn't quite the same as sparse files. If the filesystem is unaware of dedup, then it still has to allocate its own structures corresponding to the dedup'ed space, seeking to the next hole or next allocated block won't work (not that many applications are smart about holes or that MS didn't already suck in that area), etc. Dedup - even in its most absolutely simple form of just detecting zero blocks - does at least avoid the fatal problem of allocating actual disk space uselessly, but sparse files are still basically a filesystem problem and need to be treated as such.