Re: Optimizing Informix IO

In article <6gde5t$g4t$1@news.xmission.com>, "Narkinsky, Pat" <Pat.Narkinsky@rivhs.com> wrote: > >System Manifest: >INFORMIX-OnLine Version 7.14.UD1 >AIX 4.3.0.0 >IBM RS/6000 S70, 12 Processors, 8GB of memory >IBM SSA Disk Array > >We are running an Informix Based financial application with >approximately 150 simultaneous users, and have experienced persistent >performance problems. Currently, we have thrown a ridiculous (IMHO) >amount of processor at the problem and are getting adequate performance. >However, we will soon be adding users, and I am concerned at the fact >that we: >1) Have no upgrade path for hardware; we are at the top of the line >now. >2) Are still experiencing 0% Idle Time (according to sar). >3) Have to add approximately 100 users in the next six months. >Our problems are clearly IO related: examination of the output of sar >indicate we are spending approximately 80% of our time waiting for IO. > >First question: we are running with NUMAIOVPS equal to 1. Could this be >aggravating our IO problems? How can I tell if we are running KAIO? > >Second question: I've heard mention on this list to the effect "Informix >doesn't like RAID". Could someone clue me in on the considerations >here? > >Third: I've got 8GB of memory, however I am only using approximately >1.5GB. Would it be possible/advisable to try to get the engine to use >more of that memory? Will this make my checkpoints last too long? > >Fourth: One of the busiest dbspaces on the system is "tempdb1" >(according to 'onperf'). I have the following line in my onconfig file: > DBSPACETEMP tempdb1:tempdb1:tempdb2 >What is the significance of the double listing for tempdb1? Is this >probably intentional, or is it the result of a typo on the part of my >vendor? Would this account for the fact that tempdb1 is MUCH busier >than tempdb2? Should I change it? > >Thanks! > >Patrick Question the First -> under HP/UX when I bounce the engine with KAIO enabled, I get this written to the online log: DR: DRAUTO is 0 (Off) HPUX Version B.11.0 -> Using select based KAIO INFORMIX-OnLine Initialized -- Shared Memory Initialized Question the Second -> (again HP) we tried using an HP model 20 array with RAID 5. Performance was sooooo slooooow we yelled at HP so loudly they took back the array and credited full amount towards purchase of a bunch of small disks. Informix much happier with 40 2Gig disks than it was with one 80 Gig array. Question the Third -> I've never been able to figure out how adding more memory speeds things up, as long as you're not swapping and have plenty of buffers. I see no difference on our box between 1 Gig RAM and 2 Gig RAM. Question the Fourth -> Cool! Never thought of specifying the same temp space twice on the DBSPACETEMP line. Am guessing Informix treats this as it would three temp spaces, simply uses the same dbspace for the first two temps. May be way to maximize leverage when have some fast and some slow disks - specify each fast disk twice, each slow disk once. Have to try this... Hope some of this is useful... Ray Garrison