Re: Is Mirroring w/RAID 5 overkill?

Belt AND suspenders? :-) Seriously, if the data is that critical, I have started recommending to customers that they use CDR. This allows true fault-tolerance (clustered Sun servers, Veritas, First-watch, etc.). This gives a very high degree of safety. To make it even better, use CDR to mirror to a hot-site. The other options include judicious use of backups and sending your logs to tape (which you are probably doing anyway for critical data), mutiple RAID1 mirrors, combining RAID5 w/ Informix mirroring, etc. -d At 12:47 PM 8/19/97 -0500, Chuck Ludwigsen wrote: }Dave Otto wrote: }> }> Yes mirroring w/RAID5 would be overkill. In general, for }> critical systems, I prefer to use RAID-1 (h/w mirroring) as }> my fault-tolerant solution. It is usually fater then Informix }> mirroring and allows greater flexibility WRT disk layout. Some }> of the newer disk sub-systems are fast enough now, however, that }> table fragmentation is not really necessary for OLTP. Also, }> EMC2 uses disk caching routines that actually run best if you }> (intelligently) interleave your data. }> }> -d } }I agree that convential wisdom would consider this overkill. However, }consider letting Informix mirror critical dbspaces such as root and }logspaces even if you have RAID 5, though. If you take a soft error and }the chunk is marked "Down", then Informix will ask you to "Restore from }Mirror or Archive". Restore from hardware mirroring or any other level }of RAID is not an option. I went through a painful ordeal last summer }that started when our RAID controller sent an errant ERRNO=5 to Informix }for the rootdbs. Informix worked for 16 hours to get the engine up by }marking the chunk on-line but it was to no avail. Life went down-hill }from there ... but that is another story. } }> }> At 02:20 PM 8/19/97 +0000, Steven L Cooper wrote: }> }Howdy, }> }Just wondering what ya'll think? }> } }> }I have a DG AV/3600 with 24GB of RAID 5 (across 6 drives) running SCO }> }OpenServer 5.0.04 and OWS 7.2.xx. So far, Informix has run happily with }> }and without mirroring. (I learned the evils of filling the rootdb, but }> }that is another story...) }> } }> }Does Informix do anything "special" with a mirror that my RAID 5 controller }> }is not already doing? If the RAID controller goes down, a mirror is not }> }going to do me any good anyway! But, if one or two of the hard drives go }> }down, Informix would not even "know" about it. From what I have read, }> }Informix will failover to the mirrored location if a problem is detected in }> }the main location, but is that problem normally hardware related? }> } }> }Thanks for any comments, }> }Steve }> }-- }> }Ignorance can be cured! }> }scooper@thecompounders.com }> } }> } } }-- }---- }Chuck Ludwigsen <cludwigs@hotmail.com> }Database Engineer <cludwigsen@harrahs.com> }Harrah's Entertainment, Inc. }President - Memphis Informix User's Group <miug@hotmail.com> } }** My opinions are my own and sometimes conflict with those of my }employer ** } }