> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
> boun...@opensolaris.org] On Behalf Of Ulrich Graef
> Do you use de-duplication? (does not directly harm the performance, but
> needs memory
> and slows down zfs diff through that)?

Yikes.  That couldn't be more wrong.  Yes, dedup hurts performance, badly.  
Yes, in theory dedup should be able to accelerate performance, but the way it's 
presently implemented, it gets hurt too dramatically by hard disk seek/latency 
access time.  The way it's presently implemented, there is one and only one way 
dedup improves performance, which is when you read duplicate blocks, then you 
get about 2-4x read performance gain.  For all other operations - write 
duplicate, read nonduplicate, write nonduplicate...  Performance is worse with 
dedup.  As little as 2x, as high as 10x or 20x if you have sufficient memory 
*and* you optimize (because the out-of-the-box configuration is very nearly 
unusable), and infinite-x if you're having insufficient memory or you fail to 

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