Ühel kenal päeval, R, 2006-06-23 kell 10:30, kirjutas Mark Woodward: > >> > What is interesting is setting up the server so that you > >> > can service your loads comfortably. Running the server at 100% lead is > >> > not anything you want to do on production server. There will be things > >> > you need to do anyway and you need some headroom for that. > >> > >> Of course, you design it so peaks are easily managed, but unless you run > >> vacuum continuously, and that has its own set of problems, you run into > >> this problem, and it can get really really bad. > > > > Usually it gets really bad if you *don't* run vacuum continuously, maybe > > hopeing to do it in slower times at night. For high-update db you have > > to run it continuously, maybe having some 5-15 sec pauses between runs. > > And how much I/O does this take?
Surprisingly its mostly WAL traffic, the heap/index pages themselves are often not yet synced to disk by time of vacuum, so no additional traffic there. If you had made 5 updates per page and then vacuum it, then you make effectively 1 extra WAL write meaning 20% increase in WAL traffic. -- ---------------- Hannu Krosing Database Architect Skype Technologies OÜ Akadeemia tee 21 F, Tallinn, 12618, Estonia Skype me: callto:hkrosing Get Skype for free: http://www.skype.com ---------------------------(end of broadcast)--------------------------- TIP 2: Don't 'kill -9' the postmaster