A site going down for some time what should be done to save its ranking and other

[rcep]

hey folks maybe this is a very wrong section but couldnt find out the best place to post this
bit today i lose the files of a big site i got it needs lots of time to recover and get it back online
Currently i am redirecting it to another site i got so that i dont loose the traffic
What is the best thing i can do to get the minimuim losses in page rank and such stuff
Any advice :/