On Fri, May 05, 2006 at 10:19:56AM +0200, Constantin Gonzalez wrote:
> (apologies if this was discussed before, I _did_ some research, but this
> one may have slipped for me...)
I'm in the process of writing a blog on this one. Give me another day
or so.
> Looking through the current Sun ZFS Technical presentation, I found a ZFS
> feature that was new to me: Ditto Blocks.
It is (relatively speaking) a new feature. I did the on-disk work back
in October (before the initial ZFS putback), but the complete
functionality was only recently integreated (beginning of April). It
is in Nevada build 38, and will appear in S10u2.
> In particular:
>
> - Are regular data blocks multiplied by default if the disk isn't mirrored/
> raid-z'ed and there's enough space?
No, not yet. That's a future feature.
> - What are the general rules on what blocks get multiplied how often?
The rule right now is pretty straightforward:
User data blocks: 1 copy
Per-filesystem metadata: 2 copies
Global (across all filesystems) metadata: 3 copies.
My block will hopefully explain things in more detail.
--Bill
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