Re: Informix on Raid 5

Some RAID Array implementations such as Data General (or OEM) CLARiiON allow large cache (64MB) mirrored across two storage processors with battery backup to allow flush to disk on power failure. Use of a Global Hot Spare and throttle for rebuild will cut down the hit when a disk does fail. As rule RAID 1/0 with more spindles will be fastest. MO Hutch Hutchison <hutch@gnorth.com> wrote in article <32F8A9E6.2B19@gnorth.com>... > > My programmers tell > > >me that the system would be faster useing a multidrive config. than with > > >Raid. Please respond with any experiences or knowledge regarding this > > >subject. > > > > > > > I believe RAID 5 is the version which has very poor write performance. > > This is because all of the parity info is stored on one disk. This > > means that EVERY write involves one write to the parity disk. > > > > You would get better peformance with RAID 1 (i.e. mirroring) where > > not all writes involve writing to the same disk drive which becomes > > a bottleneck. > > > > -- > > David Williams > The real issue is what happens when there is a disk or controller failure. > If you choose Raid 1 mirroring with a pair of controllers and each disk on > the first controller matches a disk on the 2nd controller, then any disk > or controller can fail without loss of data OR PERFORMANCE. With any Raid > parity implementation there is an extreme performance penalty until the > failed component is replaced and it's data is resynced. > > Cache will imporve small write performance, but where do you want to > spend your money? On cache or additional disk space? Keep in mind, the > database vendors want your writes to be on disk. Your most critical data > in your logs should not be buffered when the power goes off... > > -- > Robert "Hutch" Hutchison Email: hutch@Gnorth.com > Senior Consultant Voice: 614-890-9999 > Great Northern Consulting Services FAX: 614-899-1807 > 10265 Covan Drive, Westerville, OH 43082 >