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Estimation of RAID Reliability
Redundant Array of Independent Disks (RAID) is a method to combine several disks to one data storage device.
There are various ways to write data on the array member disks that allows to achieve different goals.
You can see relationships and limitations of various layouts here.
More complex data layouts make reliability estimation difficult and sometimes introduce layout-specific quirks.
Obviously, if there is no redundancy, the reliability of multi-disk array is less than that of a single disk.
Use the calculator of RAID 0 reliability to get an estimation of how bad your RAID 0 is.
Even if an array is fault-tolerant, the reliability of a single disk is still important.
For example, in RAID 5 there is an URE issue and the probability to encounter such a problem is greater
than you might have expected.
More complex array configurations, e.g. RAID 10, RAID 50, and RAID 60 can continue working when two or more disks fail.
You can calculate the probability to avoid data loss when several disks fail simultaneously in the array using
this RAID X0 failure calculator.
If that's already too late for you
The above calculations are useful if you are planning a new RAID, or if you have a working one and you came here to find out what to expect.
If your RAID has already failed, the failure rate calculations are useless.
In this unlucky case, consider visiting any of our sites discussing RAID and recoveries from failed RAIDs: