Product : StorPool, StorPool [SDS]/19.01, x86
Feature : Block Failure Protection, Reads/Writes, Data Availability
Content Owner:  Herman Rutten
Fault Sets
StorPool protects data by keeping number of copies (1, 2 or 3) in different servers or racks. The default is 3N. This means that for example in a 5-node cluster any 2 nodes can be lost without impacting availability.

In larger StorPool clusters (e.g. 12 nodes in 3 chassis), StorPool can be configured to store replicas (copies) in different racks or different chassis, tolerating entire chassis or rack failure.

Fault Sets: By default StorPool uses a placement policy that distributes user’s data on as many physical drives and servers as possible in order to increase performance and minimize the impact in case of a node failure. When some storage nodes are interrelated and there is a higher chance to fail simultaneously, the placement policy can be tuned by defining "Fault Sets" - a set of nodes that have a higher probability to fail simultaneously. When fault sets are defined, StorPool will place data on different Fault Sets - in other words there is only one copy of the data in a particular Fault Set. By leveraging Fault Sets a storage cluster can be arranged for example in racks, where each rack represents a separate Fault Set. If an entire rack fails, the placement policy will guarantee there are at least two available copies of the data that reside on the remaining racks.