We're looking into putting up a wiki or CMS for internal use by our IT department. One of the big things we want to use it for is disaster recovery procedures.

Given that a disaster, such as a power or network outage, might render the wiki inaccessible, it seems sensible to to host the wiki in two places so that if one is inaccessible, we can fall back to the other.

Are there any wikis or CMSes that synchronize (or an alternate way to achieve a similar end)?