Ok, that makes it easy :) ... it won't work at all. The SAS 5/iR supports RAID and non-RAID (when left unconfigured); the PERC does NOT support non-RAID ... RAID and non-RAID are not compatible, even if you were going from a SAS 5/iR to a SAS 5/iR that supports both. When drives are configured in a RAID array, it writes RAID metadata - configuration information - at the beginning of the disk (where non-RAID controllers write partition information), so if you plug in the non-RAID disk to the PERC, the PERC will not see any RAID metadata and will assume the disk is empty (not recognizing or caring about the non-RAID disk partition information).  Likewise, when you put a RAID disk on a non-RAID controller, only RAID metadata is seen where the controller is expecting to see the partition layout of the disk, so it will also assume the disk is empty. Long story short ... you can move your SAS 5/iR controller to server B or you can backup/restore files after reinstalling the OS on the RAID controller.
 I am not 100% on this so hoping this can be easily answered.  I have two almost identical Poweredge 1900 servers. We will say... server A and server B Server A I am currently using and would like to transfer my drives over to server B.  The OS is server 2008 R2 Standard. I am using the server for file storage and a web forum.. So nothing crazy. Basically I would like to sell server A and use server due to the fact the casing is in a little better shape and it has a better raid card along some extra Nic's. I don't want to go through all the hassle of swapping cases and cards.. Figure it would be easier to just swap drives..   I understand processors have serials and it comes down to  licensing issues on the OS.  However, should I be able to just pull drives from Server A and place into server B as long as the motherboard and processors are identical?     Motherboards identical  Processors identical  memory identical  raid cards  Server A is Dell SAS5/ir(GU186) and server B is a PERC5/i(GT281)  I hope to be able to put the drives into the new server and the OS boot up without much issue.. Or is this going to turn into the OS crashing when it tries to load?  Thanks for the advice!   
Two identical servers swap drives