Based on this question about RAID-5 for 5 disks: Two disks failed simultaneously?
Sorry if I butcher some of the terminology
Why is a double disk failure an issue for a 5 disk Raid 5 configuration? Even with 2 disks offline, I still can access the sections (terminology?) A, B, C, D and E. Assuming there is no disagreements (terminology?) between (D1 and D2) OR (E1 and E2), I don't see why a double disk failure couldn't continue to work and rebuild 2 new drives.
If you lose more than a single disk in a RAID 5, your array has been irreperably damaged in some way. In most cases, the data is entirely destroyed in your case if you're not an expert at recovery, or if you are unwilling to ship it off to a recovery outfit. - SmallLoanOf1M https://serverfault.com/a/834147/348076