You must divide because the alternative with the sand hardware would be to run 5 nodes on a 3TB disk each. Those nodes would share the same traffic and thus hold 1/5th of the data and have 1/5th of the held back amount. If you lose 1 HDD you only use 1/5th of the amounts you mention. Not all of it, the other nodes would work just fine still. And of course you also still have 3TB of additional space to share.
You may have lost nothing so far, but raidz1 isn’t perfect. There is still a non-0 failure rate. There is a reason raidz2 and raidz3 exist. Both of which also have non-0 failure rates. And while that risk is much smaller, the impact of that loss will be much larger, because you’re losing 5x as much data and held back amount.
That thing was a disaster. Leading to class action lawsuits. Yes I think you’re cherry picking the wrong examples again. But this is not at all an argument for raidz1. An array with those disks would still have a significant failure rate, especially if the HDDs were bought in the same batch. And it would take all data with them instead of just the disks that failed.
Yes, but that same scale means it also averages out. Especially if you mix drive models to spread the risk. And currently that averages out below 2% annual failure rate.
Don’t just claim this. Prove it! Show your calculations.
Same here, show your calculations.
Edit: btw, I already did the calculations a long time ago here. Do I need a raid or mirrored array - #11 by BrightSilence