I bought this some time ago... I guess it's been 7-8 years now... and one of the HDs has failed. I configured in a RAID 2 mirror, so my data is intact, but I need a replacement drive. The drive I pulled is 5400, but can the Cloudstor accept a 7200 replacement drive? Do I need to upgrade the healthy drive to a 7200 also? Or am I stuck with 5400? Bothe drives are/were 2TB. What happens if I upgrade to 4TB each drive? Thanks!