Re: Is Mirroring w/RAID 5 overkill?

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 **