On Thu, Aug 2, 2012 at 3:39 PM, Richard Elling <richard.ell...@gmail.com> wrote:
> On Aug 1, 2012, at 8:30 AM, Nigel W wrote:
>
>
> Yes. +1
>
> The L2ARC as is it currently implemented is not terribly useful for
> storing the DDT in anyway because each DDT entry is 376 bytes but the
> L2ARC reference is 176 bytes, so best case you get just over double
> the DDT entries in the L2ARC as what you would get into the ARC but
> then you have also have no ARC left for anything else :(.
>
>
> You are making the assumption that each DDT table entry consumes one
> metadata update. This is not the case. The DDT is implemented as an AVL
> tree. As per other metadata in ZFS, the data is compressed. So you cannot
> make a direct correlation between the DDT entry size and the affect on the
> stored metadata on disk sectors.
> -- richard
>
It's compressed even when in the ARC?
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