Windows Storage Spaces - a useful replacement for RAID6?

Solution 1:

Windows Parity Spaces are dog slow and (according to Microsoft) aren’t designed for anything except archive workloads. Microsoft keeps trying to improve write performance say implemented log missing from the hardware RAIDs, but lack of the battery-powered write back cache takes away all the fun. You can however try to improve writes by telling Spaces you have UPS.

https://docs.microsoft.com/en-us/windows-server/storage/storage-spaces/deploy-standalone-storage-spaces

Set-StoragePool -FriendlyName -IsPowerProtected $True

Another point is to use ReFS and Storage Spaces combined into so-called Mirror-Accelerated-Parity, writes will end up inside SSD tier to die on HDD tier later.

https://docs.microsoft.com/en-us/windows-server/storage/refs/mirror-accelerated-parity

http://knowledgebase.45drives.com/kb/kb450193-creating-mirror-accelerated-parity-volumes-and-storage-tiers-in-storage-spaces-windows-server-2019/

Unfortunately this isn’t 100% supported scenario for anything except Storage Spaces Direct (which is another can of worms on its own).

I’d suggest Linux MDRAID+XFS due to its stellar stability and lots of proven deployments or old stock LSI hardware RAID card from eBay if you absolutely need to stick with Windows Server OS.

Solution 2:

"Windows Storage Spaces - a useful replacement for RAID6?"

If by "RAID6" you mean "I hate my data and want to get to it in as slow a way as possible" then yeah, sure - we lost 62TB of data to it at one point, luckly had a backup of it all but never again.

EDIT: Don’t trust to Windows software RAID, don’t trust to double parity hardware RAID of a great capacity, always follow 3-2-1 backup rule and “In backup we trust”.