Of any feature storage administrators could claim to be the most important of a SDS solution, it would arguably be High Availability (HA). Modern business practices demand unprecedented levels of data system uptime and data availability as down time carries a significant cost in lost productivity, sales or customers. QuantaStor's High Availability technology ensures business continuity in the event of a system failure such as a power outage, appliance hardware failure, software crash, or in some cases human error.

QuantaStor SDS High Availability Key Features

Automatic Failover
QuantaStor's SAN/NAS based failover is one of the fastest in the industry, made possible by highly parallelized HA failover system and IO fencing that ensures quick failover of ZFS-based Storage Pools. Appliances in a High Availability group also maintain a continuous "heartbeat" and provide a secondary path to disk storage in the event of a system failure. This transfer of responsibility is seamless to the end user and does not require any administrative intervention. 

Data Replication
QuantaStor achieves High Availability by making multiple copies of data that are spread across multiple servers in a cluster to ensure there is no single point of failure. Turn off any node, or in some cases even multiple nodes, and there’s no downtime and near instantaneous fail-over of workloads. Get the speed, reliability and features including snapshots, cloning, thin provisioning and massive scalability all on commodity hardware that can be expanded with RAM and solid state drives (SSDs) to accelerate throughput and IOPS performance.

Simplified Maintenance
Once a High Availability configuration has been established it can also be used to provide business continuity during routine maintenance or software upgrades. The system administrator can manually "fail over" the system to the secondary site and service will resume on the failover site.

Further Reading:
Deploying a High Availability Storage Cluster with GlusterFS
The Future of High Availability in Software Defined Storage: Ceph and GlusterFS