Agreed. Sadly, I *did* have both expansion and RAID level change capabilities on my (probably expired) h/w card. Yes, sync migration took a time but being a true RAID card it was largely irrelevant to both my own and the site's needs. Whereas SME's software RAID sync migration latency is another matter altogether... particularly for several TBs. The multiple CPU cores doesn't seem as helpful as the pundits would have everyone believe. Yes, I still do have my three 36GB 15k Raptors (for the SME OS) as a hangover from those happy times when 'the data' was stored separately on the h/w array card. And you're right about the time assessment ~ over a week IIRC;~)
The bulk data stored by SME is the backup not the source, so the RAID element isn't mandatory per se but a desirable flavour if available. I don't have the finance to readily support what you suggest despite its temptation. A while back I was centralising backup resources but I can't support the sheer numbers or logistics, so will have re-orchestrate the flow of data on a more distributed and sustainable basis. I try NOT to entrust anything to RAIDx, it's actual redundant copies that counts in my book. And all transfers are a function of what can be transferred across the gigabit SMB/intranet bottleneck.
Right now I have to get off what I fear might be the start of 'the slippery slope' caused by a succession of failures. I've much too much data flying about when it should be archived offline ~ long story ~ was expecting BD to arrive to cope with this sort of eventuality somewhat earlier.
Thank you again for your timely intervention, thoughts and good wishes.