I am at a point where my HDDS in my QNAP 4x bay will start to fail again. I have one that needs replacing now but the others are all of simllar age and will start to go one after another as they did last time. I am thinking of ditching HDD in favour of SSD as they have come down a lot in price, but cant afford to replace all of them. I have them all currently as raid 6 so I assume mixing drive formats is not the best practice? Any recommendations on which drives may be better suited to a NAS if I go to replace them all currentyl have 4 x 2tb?
If you can, drop RAID 6 and go for mirrors (RAID 1), and later on get a spare drive. In my experience, a much better experience all round. Operates without degradation if a drive fails, quick to re-silver, and easy to increase capacity without starting over.
That will drop my capacity though and not what I was asking.
Not if you buy larger disks. Anyway, just giving you an option to consider given the cost of drives, and you could always add another mirror to the pool if capacity was an issue later.
If you can don’t run the NAS at capacity. Try to have one disk as hot spare. So the NAS can handle critical situations on its own.
Larger ssd pushes it up way too much in cost i would need 2x3tb which is near to 500 without having the mirror across the 4 bays . Sorry makes no sense to me to not use my drives capacity.
Sure. Depends on use case and model chosen.
Call me cheap, but spinning disk is just fine for my file server. 
It is for mine really and it’s cheaper. I’ll most likely just replace it one for one as it will be still massively cheaper even if I replace all 4 over next 12 months. SSD is overkill it’s not doing any real-time ops and is just a backup server for my music and photos and docs.
Hello, I have 2x4 TB SSD WD Red in my NAS and 1x in my S40 Antipodes. I previously had two 6TB HDDs in Raid1. The exchange to SSD brought a little smoother operation after starting the APP. The NAS is also “only” music storage.
I’m considering building a Samsung 8TB SSD in the S40. Today I pay as much for the 8TB SSD as I did for the 4TB WD Red.