Re: Database and RAID

Some of the logical volume managers also support 'split mirrors'. The EMC Symmetrix supports extra mirrors (locally in the same box and/or remotely over fibre) that can be split fairly quickly. One nice option is that the 'split mirrors' can then be assigned to a secondary host where another Informix server can be started for testing, reporting, DSS, oncheck, etc. Also, the Symmetrix re-silver (or restore in case of DB corruption) of the split mirrors can be fairly fast because (a) it only copies the tracks that were modified since the split (not the entire mirror) and (b) the host and SCSI/fibre paths are not involved. Doug > This was intended for use as a VERY fast method. Namely in combination > with 7.30's support for multiple mirrors. You can have two mirrors > defined for each chunk, take the engine to external backup mode, > disable one set up mirrors, put the engine back online, backup the > disabled mirrors offline, reenable the secondary mirror. Alternatively, > you can just leave the additional mirrors offline and use them as the > backup directly then disable the other mirror to use as backup and > bring the original backup mirrors back online to be caught up. This is > great for EXTREMELY large databases as an "archive" only takes about > 2 minutes, the time needed to disable one of the mirrors and reenable > the other, and if it can be scheduled at a time when there will be no > updates there will be no effect on production. > > Just FYI > > Art S. Kagel >