Re: Hardware RAID vs OnLine Mirroring

In article <6gaf8b$o4m$1@news.xmission.com>, Glyn_Balmer_at_erith@smtpgwy.supertension.com wrote: > > I have picked up on Dennis Harding's response regarding > Informix-OnLine and RAID. > > We are shortly upgrading our server, UNIX and OnLine engine to an ICL > (Fujitsu) Teamserver, SCO UNIX Openserver 5.0 and OnLine 7.2x. Our > intention (at this stage) is to use hardware RAID (5) (Mylex). We > shall have 5*4Gb disks, less 1 for RAID parity, giving 16Gb database > disk space. This will be raw disk. My questions are as follows :- (1) > Are there any known problems running OnLine 7.2x using raw disk and > hardware RAID ? (2) Would we be better off forgoing the hardware RAID > and using OnLine 7's mirroring ? > > Any comments, particularly in view of Dennis' comment ("In general, > Informix does not like RAID") would be very welcome. > > Regards > Glyn Balmer > I.T. Consultant > BICC Cables Limited > Erith Kent UK Biggest problem we ran into was the specific RAID unit we were using (HP model 20 disk array - aka Nike disk array) was very stubborn about how you configured it. Informix likes to see multiple devices for parallel scans - RAID system looked like maximum of three devices, each of which was huge. Result was terrible bottleneck on I/O. Even with cache maxed out (32 Meg on that RAID box) disk performance was on order of 10% of what we achived on the same exact system using multimple slower, single ended 2 Gig disks. Got rid of RAID went back to lots 'o little disks - Informix and customers much happier. Stay away from RAID 5 unless your uptime/hot swap/disaster recovery issues are far and away more important that performance. Ray Garrison