[OpenIndiana-discuss] ZFS pool slow as molasses

[Jesus Cea]

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On 06/10/10 10:23, Albert Lee wrote:
> The problem here is probably from having dedup enabled. Disabling it
> does not affect the existing data, which has already been
> deduplicated. Reading any of this will incur a deduplication table
> lookup, which can be quite expensive in terms of random seeks (you can
> check with DTrace, see /opt/DTT/disk/seeksize.d). I've also seen poor
> performance on a pool that was previously full.

How can deduplication affect reading performance, beside disordering the
data around the disk?. I don't see the point of accessing the
deduplication table for file reading.

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