I'm currently looking into RAID 5 for my growing data for my home PC and some things are still unclear to me. I currently have each of my drives backed up by an additional "backup" drive and I only use custom scripts to back up my data frequently. I currently have 4 drives of data, plus 4 drives to back these up (plus 1 junk data drive without backup). Most of them are external USB drives. I'll soon be running out of storage again so I'm looking at maybe better options.. I've had my current lazy backup strategy going for about 15 years. Unfortunately my main limiting factor is cost and I can't simply buy a whole set of new more-suitable drives to do whatever would be the best option. Just needing double the drives every expansion is already expensive.
Thus I've been looking into RAID 5 and considering setting up three RAID 5 storages using my 9 existing drives (mostly because only 3 drives each have the same size). I would be using the Windows 10 storage pools parity option for this and I'll refer to it as RAID for simplicity.
Questions
1. I read that (obviously) USB drives are not a good option for RAID due to throughput limits, which I understand. But I found nowhere to what extent. Would I expect a major read/write slow down compared to a single drive? Or would the RAID 5 just be "as-slow" as the slowest USB drive in the RAID? Or could there even be a slight speed up?
2. I don't understand the statement I find everywhere that a single URE (unrecoverable read error) in addition to one drive failure can mean a loss of the whole RAID. I've encountered partial drive failures, but never has one of my drives just completely died without warning in the last 15 years. If only some sectors are corrupt, would I not just lose the data on the stripes corresponding to those sectors, as opposed to the whole RAID?
3. Assuming I only have some sectors fail on one drive, how does the rebuilding work? Do I have to completely remove the affected drive and rebuild it all? Or can I use a 4th drive outside the RAID, copy all non-corrupt sectors to it, and only rebuild the corrupt ones, also writing it to that 4th drive? Even more importantly, what about the case when 2 sectors on 2 different drives, but also in 2 different RAID-stripes go corrupt? I don't see why this would be a data loss, other than the Software not being able to handle it. But so far what I read seems to suggest that this is a data loss. If this is the case I don't think I will use RAID, as this seems quite unreasonable..
4. To my understanding the highest risk comes when one drive fails completely, and I have to read all the data from all the other drives to rebuild it. It did not become clear to me how stressful this is. In my current setup, I verify my data every so often by hashing every file on the data drive and the backup drive and comparing it to a list of hashes saved elsewhere. I assume this is just as stressful as rebuilding a RAID drive?
Thanks for any help