What your saying is a falsehood, and a persistent rumor started by a bad paper and easily disproved. The individual disk capacity has nothing to do with the dri

What your saying is a falsehood, and a persistent rumor started by a bad paper and easily disproved. The individual disk capacity has nothing to do with the drive failure rate. First, while RAID isn't a "safeguard", the idea that there is a high probability of raid failure during a rebuild has been repeatedly proven to be false as long as proper data hygiene is maintained. For the most part the chance of a second disk falling out during the rebuild is exactly the same as any other day regardless of capacity. Put another way, if your scrubbing (or just accessing the data) frequently enough to avoid having silent bad sectors the idea that there is a high probability of a drive loss during the day or two it takes to rebuild an array would also result in drive losses on a nearly daily basis. So unless your constructing a single RAID5 array out of ten thousand plus disks, if the MTBF numbers are anywhere close to realistic, drives in a single array aren't going to be failing at a rate high enough that the chance of a double fault not caused by something symptomatic across the entire line of drives (say a firmware that wipes the drive after X power on hours, in which case no level of redundancy will save you) is a real worry. So, the rumor is based on the idea that your increasing the RAID rebuild time from a couple hours to days/weeks on end due to the larger capacity. But this is also false, because as density increases so has the sequential throughput of the drives. AKA comparing a ~ten year old 4TB drive doing ~100MB/sec vs a modern 8TB drive doing 200MB/sec. There are some non-linearities due to the number of platters and the rate of TPI vs BPI increases but generally platter count is somewhat constant and TPI and BPI are both increasing. Now if your hitting internal RAID limits because your running modern drives on old controllers which cannot rebuild at the drives peak throughput that is a different problem. Bottom line, your doing it wrong if RAID5/6 isn't increasing both actual as well as theoretical availability. The MTBF numbers are published to give a baseline on what the expected failure rates are.