Re: Informix vs. AIX Mirroring

Jack Parker - Hewlett Packard, DMD/IS Boise, Idaho, USA wrote: >I disagree. Filesystem damage can 'take down' a primary drive. Since >it is generally a raw device - hte Unix mirroring will never notice a need >to switch over where the Informix mirroring will. Where we have used >Informix mirroring we have been very happy with it. Where we have not >we have had this sort of problem. We use mirroring on an HP-UX system and have done it both ways. We are currently doing it at the O/S level and have had no reasons to switch back. HOWEVER: We have found the HP-UX (specificly 9.0X) was not very good at detecting drive failures and taking the failing disk off line. This is exacerbated by the fact that HP-UX mirroring reads from the least busy drive. We have had several instances where a drive began to fail on either read or write and the O/S continued marrily along its way picking up bad data on one drive and corrupting the data on the working mirror as well. This may be the same kind of problem which has caused Jack's headaches. HP-UX mirroring is supposed to work on both raw and cooked versions of a device and in our experience it was with a cooked device that the O/S failed to recognize a disk failure. Incidently, I tried to point out to HP that something was wrong with their hardware/software design if a drive was failing and the O/S could not take appropriate action in a mirrored environment. I also pointed out that if I were in banking I'd be real upset. The response from HP was -- What do you expect from UNIX. Dave Cooley Colby College