Re: Informix on Raid 5

Mike South wrote: > > On Mon, 3 Feb 1997 21:06:15 +0000, David Williams > <djw@smooth1.demon.co.uk> wrote: > > >In article <01bc0fdb$eeed12e0$1d6a93c0@dashforcash.chrims.com>, * > ><smitty@chrims.com> writes > >>Hello > >> I have a question regarding increased performance from the informix engine > >>when used on a RAID 5 system in a sco unix environment. 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 > > This is only true if you are NOT using a Fast Wide SCSI2 or similar > controller. With a good caching controller RAID 5 canm arguably be > way faster than RAID 1 due to parallel write capability. (Table > fragmentation without the hassle) > > Michael The original post did not mention, where he expects performance, READING, WRITING, PARALLEL OPERATIONS? . I have a customer using ALPHA SERVER with RAID5 and the performance is acceptable (Not Excellent), INFORMIX will gain much performance for parallel reads and fragmentation without a RAID system of any level. Note that some RAID5 systems will offer a hardware partition capability, which will help informix fragmentation, and parallel operations, For OLTP systems, you can obtain benefit by using multiple masters arrays of smallest economical capacity and from largest possible cache to disk capacity ratio, This is because OLTP data is I/O sensitive. Multiple arrays on single SCSI bus will increase I/O rate but not throughput (Complex data is throughput sensitive), but Multiple arrays on multiple SCSI busses will increase I/O rate AND trhoughput provided the host system is sufficiently powerful. Regards, ------------------------------------- Mario Estrada | Sisteco,S.A. Informix Support | Phone(502) 3340214 Department | Fax(502) 3348447 -------------------------------------