On Fri, May 7, 2010 04:32, Darren J Moffat wrote: > Remember also that unless you are very CPU bound you might actually > improve performance from enabling compression. This isn't new to ZFS, > people (my self included) used to do this back in MS-DOS days with > Stacker and Doublespace.
CPU has been "cheaper" in many circumstances than I/O for quite a while. Gray and Putzolu formulated the "five-minute rule" back in 1987: > The 5-minute random rule: cache randomly accessed disk pages that are > re-used every 5 minutes. http://en.wikipedia.org/wiki/Five-minute_rule They re-visited it in 1997 and 2007, and it still holds: > The 20-year-old five-minute rule for RAM and disks still holds, but for > ever-larger disk pages. Moreover, it should be augmented by two new > five-minute rules: one for small pages moving between RAM and flash > memory and one for large pages moving between flash memory and > traditional disks. http://tinyurl.com/m9hrv4 http://cacm.acm.org/magazines/2009/7/32091-the-five-minute-rule-20-years-later/fulltext Avoiding (disk) I/O has been desirable for quite a while now. Someone in comp.arch (Terje Mathisen?) used to have the following in his signature: "almost all programming can be viewed as an exercise in caching." _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
