Pear Atomicicy on package Install

I'm trying to develop a deployment strategy for our company which uses multiple in house modules which are going to be formed into packages which are then deployed to our clusters on the data-centers. I haven't found any information about how PEAR deals with atomicity for install/upgrade and my experiments so far indicate it'll install happily but in an error eg memory overflow, invalid MD5 etc it leaves a half stable upgrade.
Does anyone have any approaches which may solve this, or avoid the problem in the first place?

Also, can Pear perform manual rollbacks, for example a valid module has been uploaded and is syntactically correct but implements business rules incorrectly and needs to be removed and replaced with previous version, can pear do a "pear rollback" or do we need to explicitly define the previous version for "install -force"

Cheers

Warmfusion