> OK, I'll bite; it's not like I'm getting an answer to > my other question.
Did I miss one somewhere? > > Bill, please explain why deciding what to do about > sequential scan > performance in ZFS is urgent? It's not so much that it's 'urgent' (anyone affected by it simply won't use ZFS) as that it's a no-brainer. > > ie why it's urgent rather than important (I agree > that if it's bad > hen it's going to be important eventually). It's bad, and it's important now for anyone who cares whether ZFS is viable for such workloads. > > ie why it's too urgent to work out, first, how to > measure whether > we're succeeding. You don't have to measure the *rate* at which the depth of the water in the boat is rising in order to know that you've got a problem that needs addressing. You don't have to measure *just how bad* sequential performance in a badly-fragmented file is to know that you've got a problem that needs addressing (see both Anton's and Roch's comments if you don't find mine convincing). *After* you've tried to fix things, *then* it makes sense to measure just how close you got to ideal streaming-sequential disk bandwidth in order to see whether you need to work some more. Right now, the only reason to measure precisely how awful sequential scanning performance can get after severely fragmenting a file by updating it randomly in small chunks is to be able to hand out "Attaboy!"s for how much changing it improved things - even though this by itself *still* won't say anything about whether the result attained offered reasonable performance in comparison with what's attainable (which is what should *really* be the basis for handing out any "Attaboy!"s). Rather than make a politically-incorrect comment about the Special Olympics here, I'll just ask whether common sense is no longer considered an essential attribute in an engineer: given the nature of the discussions about this and about RAID-Z, I've really got to wonder. - bill This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
