tadawson Elite Veteran Location: Lewisville, TX
| For high availability solutions, there are far better solutions than VMWare. VM is great for test environments and things that don't need the full "grunt" of a single box. For HA, solutions like PolyServe or are far superior, and can actually allow parallel processing on a lot of apps. Using a quality database with data integrity checking and recovery goes a long way too - if a system is properly designed, more than one backup a day is excessive and should not be needed.
Oh, and while I think they upgraded it beyond this issue (or plan to), VMWare's VMotion has (had?) a pretty tough limitation - both systems need to be up to get VMotion to work. IE, if one system dies, VMotion can't do anything to help . . . it's more of a load balancing tool than an HA tool . . .
And regarding RAID, when you get to "real" RAID - IE, not the embedded junk that comes with servers, but rather a real, dedicated, fully redundant system, RAID-5 (and now RAID-6, like 5 with dual parity) pretty much rules the market - RAID-1 has pretty much been abandoned in larger installs due to the wasted disk space, and having no additional resiliency over RAID-5 (or 6). For what it's worth, one of the main "pros" of RAID-6 is the scenario that tchavei described - secondary drive failures on rebuilds - the dual parity gets you over that hump. That, and using commercial quality disks and not the "home pc" junk makes a lot of difference in reliability as well. They cost more, but live a LOT longer . . .
- Tim
The more I touch electrics, the more I grow to hate them . . . . |