I have a home server running Centos 7 that I'm using to host various different servers - a webserver, two Minecraft servers, and a PLEX server. Currently I have a 4TB HDD which serves as the primary storage, housing the OS and all files, and a 240GB SATA SSD which I'm using as a cache drive with Lvmcache. I've begun to run out of space on the 4TB disk, so I'm looking for a way to migrate this single disk to RAID 5 without needing to reinstall and reconfigure the OS and all software. I've chosen RAID 5 as it appears to be the best balance of price, performance, and redundancy for me.
If I were to purchase 3 additional drives and build a RAID 5 array with them, is there any possible way to clone the data and OS from the existing drive onto the array, verify that this worked correctly, then erase the single drive and join it into the array? Alternatively, should I purchase an additional, smaller drive to house the OS and clone it there, then simply use the RAID array for mass storage?
I have never previously had the occasion to use a RAID array, so I have no prior experience with them. I did find a piece of software called "Raider" that looks like it might possibly be up to the task, but, again, I have no experience with it; better safe than sorry!