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#11
I would suggest installing Hard disk sentinel, it is still free I think at the moment. This would tell you exactly what you have and which drive is failing and why.
Other than that if you can afford it I would go for either two 512Gb SATA SSD's or one 512Gb SATA SSD + a 1Tb (or bigger) SATA HDD. Since you have such large backup solutions already in place you don't really need large storage in your machine, unless you regularly edit 4K video footage.