I am archiving a vast amount of media files that are rarely accessed. I’m writing large sequential files, at peaks of about 100MB/s.
I want to maximise storage space primarily; I have 20x 18TB HDDs.
I’ve been told that large (e.g. 20 disk) vdevs are bad because resilvers will take a very long time, which creates higher risk of pool failure. How bad of an idea is this?
You’ll be fine. You have three disk redundancy. If one of the disks fail you’ll still have two disk redundancy during rebuild. You could lose 2 more drives during rebuild and still have all your data. What is the likelyhood of three disks failing during rebuild?
The likelyhoods are calculated with multiplication. If the likelyhood of one disk failing during rebuild is 0.01 then the likelyhood of two disks failing is 0.01 * 0.01 = 0.0001. Three disk failure would be 0.01 * 0.01 * 0.01 = 0.000001. One out of a million.
It’s way more likely to ruin the files by accidental deletion, destructive commands, software errors, massive hardware failure like your power supply failing and destroying all your drives at the same time or your house burning down.