Re: OnLine on RAID - what's the truth?

In article <memo.19981014141509.39963D@andykent.compulink.co.uk>, andykent@cix.co.uk (Andy Kent) wrote: > I have a client who's attempting to run OnLine 5.10 on a Compaq RAID 5 > architecture. I know little about RAID (other than the basic levels and > what they are designed to do), except that early implementations of > RAID 5 were DISASTROUS for OnLine's performance but that newer > products, with their various smart disk management capabilities, are > claimed to be as quick as a raw disk-based system, provided you choose > the right RAID level for each component (e.g. don't put the logs on > RAID 5!) > > The Compaq website makes ambitious claims as to how well their RAID > systems should perform with an RDBMS (of course). > > However, the "Informix-OnLine Dynamic Server Handbook" by Carlton Doe > today states "RAID levels 5 and 6 are the slowest of all the RAID > levels. You should only implement this level if access speed is not an > issue ... The I/O throughput for these levels is very low because of > the disk contention involved ... The one advantage these two RAID > levels have is that they provide a decent degree of data availability > at about half the disk cost of [RAID 1]." > > What's the truth? > Can anyone speak from experience on this subject please? > > -Andy Kent- > Bristol, England. > IMHO hardware based RAID 5 outperforms software based RAID 1, as long as you got reasonable amount of RAM in the RAID unit. But hardware RAID 1 is quicker than RAID 5. Again my personal view is a hardware solution is always faster than a software solution and wrt to RAID this has proved, to me at least, in practise. If you've got the time try both and base the decision on what you find. Paul Watson # I don't suffer from WF Software Ltd. # stress, I'm just Tel. (+44) 1436 674729 # a carrier Fax. (+44) 1436 678693 # www.wfsoftware.co.uk