Re: HP vs Informix mirroring

Ed Bidinotto <eb06709@po1.cobe.com> wrote in article <350EEDF9.187C@po1.cobe.com>... > We are running HP-UX 10.20 with Informix 7.23UC1 and are looking at > either working with Raid 5 or going with scsi mirroring. We have seen > great performance with raid 0+1 on another server and have not had great > results with raid 5 so here's my question to the masses. > > Does anyone have any stats on performance or even recommendations as to > which one of the above is better? I've always heard that if you are > going to be mirroring - then go with Informix however I think that > person just said that because they didn't know anything about HPUX > mirroring. I don't know the pros and cons, hopefully someone does. > <snip> It has been my experience that HP Mirroring through LVM does a better job of distributing disk reads between the mirrored drives. Informix mirroring takes a rather simplistic approach to distrbuting reads. Anything from the first half of the chunk is read from one drive and anything from the second half of the chunk is read from the other drive. With LVM, which ever disk is not busy at the time of a read request is used no matter where the data is located. If both drives are busy, then the first available one is used. I'm not sure, but I think some seek optimization is done as well, prefering to read from the disk which has its read heads closest to the data to be read. In any case, disk utiliztaion for both halves of a mirrored pair will usually be close to equal with LVM. With Informix mirroring it is not uncommon to see one drive at 100% utilization while the other disk sits idle. HTH Irwin Goldstein Objective Software Systems, Inc. Remove anti-spam characters from return address if replying via e-mail.