Value in separate scratch disk?

I am building a i7-8700 Coffee Lake Hackintosh to take over Resolve duties from my long-in-the-tooth Mac Pro. Can anyone advise on ideal media setup?

I was intending to go for:
- 256GB NVME System and app drive
- 1TB Scratch/render NVME drive
- 4x 3TB 7200RPM drives in RAID 0 for media

My main question is, is there a value in using a separate fast scratch drive with Resolve? Alternative is to just have a fast system drive and then use either the same spinning drive RAID 0 or a SSD RAID for everything else. Large SSDs are still really expensive, and realistically I'd need at least 4TB or 6TB as a media drive, even if I only kept 1-2 projects there at a time before offloading to external storage.

Media is almost exclusively ProRes or RAW from UMP, in 2K, 4K and 4.6K varieties.

(PS I'm well aware of the dangers of RAID 0 - it's a risk worth taking for me because I need the speed. Time Machine can provide redundancy and projects will be moved off the RAID as soon as they're complete.)

I'd get a second SSD for caches and/or optimized media. The rule is keeping off any media from the system drive. Spinning media are fine for ProRes and even RAW, but I'd use compressed RAW if not desperately needing uncompressed.

I'd get a second SSD for caches and/or optimized media. The rule is keeping off any media from the system drive. Spinning media are fine for ProRes and even RAW, but I'd use compressed RAW if not desperately needing uncompressed.

Definitely 3:1 or 4:1 - I don't have the space for uncompressed.

I'm unlikely to use much optimised media - so the extra drive will be mainly caches. Would it make that much difference to have a separate cache drive of super fast SSD - say NVME? And if so, how big does that need to be to work?

I don't think you'll see that much of an advantage with superfast media, the OS is adding some overhead by file management anyway. Any good SSD should do.

I don't think you'll see that much of an advantage with superfast media, the OS is adding some overhead by file management anyway. Any good SSD should do.

OK thanks - but it's definitely worth having that separate caching drive, and not caching to the RAID that is storing the media?

So setup would be:
- 250GB SSD system/app drive
- 1/2TB SSD for caching and possibly project files?
- 12TB RAID of spinning drives for video files

That makes sense?

Yes, that makes sense. It's not only about transfer speed, SSDs are so much faster in jumping to the right file.

chk the speed of the 12Tb raid, it may well be fast enough to avoid a cache disk completly
- if the 12Tb raid is 12 x 1Tb WDRedPro's on SAS to an Lsi raid controler, it will be more than fast enough for any reasonable use
- if the 12Tb raid is 2 x 6Tb WDgreen in a $50 USB3 raid houseing, well yea, a cache disk would be needed...

i do not use a cache disk, prefering 16x spinning disks in raid5, that's enough to stay well inside a comfort zone in the real world
i do mirror my OS drive on SSD's

chk the speed of the 12Tb raid, it may well be fast enough to avoid a cache disk completly
- if the 12Tb raid is 12 x 1Tb WDRedPro's on SAS to an Lsi raid controler, it will be more than fast enough for any reasonable use
- if the 12Tb raid is 2 x 6Tb WDgreen in a $50 USB3 raid houseing, well yea, a cache disk would be needed...

i do not use a cache disk, prefering 16x spinning disks in raid5, that's enough to stay well inside a comfort zone in the real world
i do mirror my OS drive on SSD's

Since I'm working within consumer i7-3700K/Z370 parameters on this build, PCI slots are at an absolute premium. RAID is 4x 7200rpm 3TB Seagates in RAID 0, but I've decided to go with the 1TB NVME scratch and a SATA SSD for system.

Should all be lighting fast compared to my current RAID which has slowed to a crawl after years of fragmentation.