Re: HP/Raid5/Performance Lessons

David Williams wrote: > > In article <330C89FB.2578@cobe.com>, Edward Bidinotto <edbid@cobe.com> > writes > >If you are running or wish to run with Raid on HP here are some things > >that we recently ran in to. > >Onstat -g sch showed the CPU vp's basically spinning their wheels.. > > See below. > >Adding additional CPU vp's or AIO vp's made things worse. > >We added 2 more CPU's, moved Rootdbs off to disks outside of the Raid, > >striped the logical logs on 2 disks outside of Raid and put Physical > >logs on their own chunk outside of Raid.. > >It got worse.. onstat -g ath showed mostly sm_reads and everyone was > >sitting in line waiting for semaphores but couldn't get any. > You do not have enough semaphores configured in the kernel - check > you're release notes and increase kernel parameters associated > with semaphores:- > > semmap size of control map used to manage semaphore sets > semmni number of semaphore identifiers in the kernel (maximum > number of semaphore sets that can be active at any one > time). > semmns number of semaphores in the system. > semmnu number of semaphore undo structures in the system > semume maximum number of undo entries per undo operation. > > E.g for Solaris Informix recommennd. > > semmap 256 > semmni 4096 > semmns 4096 > semmnu 4096 > semume 64 WE had all the SEMAPHORES in the KERNEL configuration at the recommended values. If you looked at the system it showed that very few semaphores were actually being utilized. But we did have all max values that was one of the first things we checked after talking with Informix advanced supt group. > >Even though the books say to keep CPU vps = # cpu's we've found that > Wrong! CPU vps = (# number of phyiscal cpu's) -1 is noramlly > the recommended advice. I must not have stated it correctly... CPU vps = #Physical CPU's -1 sorry... I did read that... We did increase it by one dynamically with the onmode command and watched our numbers...the load still increased. In any case, we are running very well right now. It will be interesting to see what happens when we try to go back to all Raid. Raid...kills them dead !! Sounds like a commercial huh?