To really take advantage of SSDs on a Mac, I think you need to be using a machine with Thunderbolt 3 / USB-C. Unless you are doing client-critical work, I think RAID etc is overkill. I would caution to be very careful relying on 8 year old drives that have been in regular use as they won't last forever. I can't advise on the duo drives Allan as I have never used anything like that. Thank you for being a really helpful friend to all on the forums. I am asking this here as others might be interested but if you wish you could email me direct. They are both 4 Tb drives but I would be looking at larger capacity drives to future-proof.
When Carbon Copy Cloner kicks in it is set to backup from Duo 1 to Duo 2. Just to clarify the two existing Duo drives are daisy chained with the computer so I am always working from duo 1. I have concerns that the existing WD Duo's I am running may fail completely in the near future so need to replace sooner than later. As you say the G-tech are the same company and I could investigate those but I am interested also in your thoughts on SSD's. I have been investigating alternatives as I cannot find a supplier who carries the WD duo drives for replacement of the faulty ones.
Usually when I power down the computer the drives power down too. The intermittent problem I do have is with one or both of the WD storage drives is that after closing the computer down they keep power on and I have to force the computer to close and even then the drives continue to spin. There is nothing wrong and I am not having problems with the machine so I intend continuing to use it. Hi Mick, Not Wishing to divert the thread from Paulette but am interested in what you said about storage drives in your last post. I am using two WD Duo hard disc drives for storage and backup which I purchased when I bought the late 2013 27" iMac I am still using now.