2 ms·

A modern filesystem, like ZFS, will protect against random bit errors. Raid 5/6 are still not appropriate for todays large disk sizes, but raidz3 (three parity

• yellowapple 11y ago
  Depending on the size of the array, however, even having three parity disks is likely insufficient. Using parity instead of mirroring (or a mirroring+striping approach like RAID10) - i.e. RAID3, RAID5/6, and (IIRC) RAID-Z - assumes that disk failures are rare; in reality, the probability of subsequent disk failures increases significantly once one disk failure occurs (which makes sense: unless you're mixing/matching vendors (which has its own problems), you're probably buying a lot of disks at the same time, probably from the same or similar batches, and therefore with the same failure tendencies). For things like SANs and other large arrays of disks (where the use of ZFS is more prevalent), the difference in safety between two and three parity disks is negligible. You could keep adding more and more, but at that point, you might as well just use RAID10. If you're running a smaller array, you also might as well just use RAID10 (or RAID1 if you only have 2 disks in the array, but that's playing it dangerous for the same reason why RAID5/6/Zx is playing it dangerous). This is part of the reason why ZFS supports a variety of different RAID and RAIDlike configurations. If you're using a pure-ZFS approach, I'd strongly recommend having zpool create striped mirrors (i.e. RAID10) in order to get the benefits of ZFS' data checksumming and not be susceptible to such a high risk of data loss.