On 01/07/2011 01:15 PM, Darren J Moffat wrote: > On 07/01/2011 11:56, Sašo Kiselkov wrote: >> On 01/07/2011 10:26 AM, Darren J Moffat wrote: >>> On 06/01/2011 23:07, David Magda wrote: >>>> On Jan 6, 2011, at 15:57, Nicolas Williams wrote: >>>> >>>>> Fletcher is faster than SHA-256, so I think that must be what you're >>>>> asking about: "can Fletcher+Verification be faster than >>>>> Sha256+NoVerification?" Or do you have some other goal? >>>> >>>> Would running on recent T-series servers, which have have on-die >>>> crypto units, help any in this regard? >>> >>> The on chip SHA-256 implementation is not yet used see: >>> >>> http://blogs.sun.com/darren/entry/improving_zfs_dedup_performance_via >>> >>> "Note that the fix I integrated only uses a software implementation of >>> SHA256 on the T5120 (UltraSPARC T2) and is not (yet) using the on CPU >>> hardware implementation of SHA256. The reason for this is to do with >>> boot time availability of the Solaris Cryptographic Framework and the >>> need to have ZFS as the root filesystem." >>> >>> Not yet changed it turns out to be quite complicated to fix due to >>> very early boot issues. >>> >> Would it be difficult to implement both methods and allow ZFS to switch >> to the hardware-accelerated crypto backend at runtime after it has been >> brought up and initialized? It seems like one heck of a feature > > Wither it is difficult or not depends on your level of familiarity > with ZFS, boot and the cryptographic framework ;-) > > For me no it wouldn't be difficult but it still isn't completely trivial. > >> (essentially removing most of the computational complexity of dedup). > > Most of the data I've seen on the performance impact of dedup is not > coming from the SHA256 computation it is mostly about the additional > IO to deal with the DDT. Though lowering the overhead that SHA256 > does add is always a good thing. > Well, seeing as all mainline ZFS development is now happening behind closed doors, all I can really do is ask for features and hope Oracle implements them :-). Nevertheless, thanks for the clarification.
BR, -- Saso _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
