Carson Gaspar wrote: > Richard Elling wrote: > ... > >> Carson Gaspar wrote: >> > Except sar sucks. It's scheduled via cron, and is too coarse grained for >> > many purposes (10 minute long samples average out almost everything >> > interesting). >> >> There is a world of difference between the tools needed to perform >> debugging and performance improvements vs long-term trending. sar >> is a big, warty beast, but it works reasonably well for long-term >> trending. The 3rd party tools like TeamQuest are more modern and >> do a better job -- you get what you pay for. >> > > The problem is that even for long term trending you need better than 10 > minute resolution, unless your app isn't bursty at all, or you leave a > _lot_ of headroom (or you only care about throughput and not latency). >
By default, the crontab for sa1 (/var/spool/cron/crontabs/sys) sets 20-minute intervals. This can easily be changed to suit your needs. > Sadly, most (but by no means all) 3rd party tools are resource hogs > themselves, so aren't very good for permanent resource utilization > tracking (although they can be amazing at application performance > debugging). One of the really cool things about dtrace is its extremely > low perormance impact. > Some dtrace scripts have very large, negative impacts on performance. However, I think for most modern systems, sar won't have much impact. I dunno how all of the tools affect performance, however. I suspect it varies widely. > Thus, my (trimmed in the quote) recommendation to write your own using > kstat, as opposed to relying on sar. Or go buy something, but in my > experience sar is unlikely to make you happy. > sar has lots of problems, which is why there is a market for 3rd party capacity planning tools. OTOH, most of the others aren't open source. http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/cmd/sa/sar.c I should also mention Fenxi, an open source performance analysis engine we developed for analysis of performance experiments. Again, it doesn't replace capacity planning tools, but it certainly makes experiments easier to manage. https://fenxi.dev.java.net/ I reserve my comments on SunMC for dimly lit bars... -- richard _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
