SoftNAS Dual Zone High Availability
Buurst Staff
November 04, 2020

SoftNAS SNAP HA High Availability delivers a 99.999% uptime guarantee that is a low-cost, low-complexity solution that is easy to deploy and manage. A robust set of HA capabilities protect against cloud storage failures to keep business running without downtime.   

SNAP HA monitors all storage components for potential failure and automatically takes over when necessary. It overcomes the challenge of protecting data and application availability across a cloud infrastructure, while easily integrating into existing IT deployments. 

Continuous Availability ensures your applications are always available when you need them. Multiple data paths safeguard against hardware, software and human error. 

  • Safeguard critical data against unplanned storage outages. 24 x 7 x 365 
  • Feel confident that your business is protected at all times 
  • Data protection across multiple availability zones 
  • Creating data protection with a design philosophy of simplicity and ease of use. 
  • Replicate data so there is an up-to-the-minute recovery 
  • Prevent incorrect or outdated data from be made available due to multiple failures across the storage environment 
  • Ensure your applications and storage remain available 
  • Enjoy the ability to make storage maintenance and upgrades with little or no downtime in their production environment. 

With SoftNAS you can rely on its continuous availability and highly available snapshots, replication, and the enterprise class storage services to drive your business forward. 

Several measures have been taken to ensure the highest possible data integrity of your highly available block storage system. An independent “witness” HA controller function ensures there is never a condition that can result in what is known as “split-brain”, where a controller with outdated data is accidentally brought online. SNAP HA prevents split-brain using several industry-standard best practices, including use of a 3rd party witness HA control function that tracks which node contains the latest data. On AWS, shared data stored in highly redundant S3 storage is used.  

Another HA feature is “fencing”. In the event of a node failure or takeover, the downed controller is shut down and fenced off, preventing it from participating in the cluster until any potential issues can be analyzed and corrected, at which point the controller can be admitted back into the cluster. 

Finally, data synchronization integrity checks prevent accidental failover or manual takeover by a controller which contains data which is out of date. 

The combination of tunable high-integrity features built into SNAP HA ensures data is always protected and safe, even in the face of unexpected types of failures or user error.  

SoftNAS SNAP HA High Availability delivers the availability required by mission-critical applications running in virtual machines and cloud computing environments, independent of the operating system and application running on it. HA provides uniform, cost-effective failover protection against hardware and operating system outages within virtualized IT and cloud computing environments. SNAP HA: 

  • Monitors SoftNAS storage servers to detect hardware and storage system failures 
  • Automatically detects network and storage outages and re-routes NAS services to keep NFS and Windows servers and clients operational 
  • Restarts SoftNAS storage services on other hosts in the cluster without manual intervention when a storage outage is detected 
  • Reduces application and IT infrastructure downtime by quickly switching NAS clients over to another storage server when an outage is detected 
  • Maintains a fully replicated copy of live production data for disaster recovery for block storage 
  • Is quick and easy to install by any IT administrator, with just a few mouse clicks using the automatic setup wizard 

SoftNAS SNAP HA provides NFS, CIFS and iSCSI services via redundant storage controllers. One controller is active, while another is a passive standby controller. Block replication transmits only the changed data blocks from the source (primary) controller node to the target (secondary) controller. Data is maintained in a consistent state on both controllers using the ZFS copy-on-write filesystem, which ensures data integrity is maintained. In effect, this provides a near real-time backup of all production data (kept current within 1 to 2 minutes). 

A key component of SNAP HA is the HA Monitor. The HA Monitor runs on both nodes that are participating in SNAP HA. On the secondary node, HA Monitor checks network connectivity, as well as the primary controller’s health and its ability to continue serving storage. Faults in network connectivity or storage services are detected within 10 seconds or less, and an automatic failover occurs, enabling the secondary controller to pick up and continue serving NAS storage requests, preventing any downtime. 

Once the failover process is triggered, either due to the HA Monitor (automatic failover) or as a result of a manual takeover action initiated by the admin user, NAS client requests for NFS, CIFS and iSCSI storage are quickly re-routed over the network to the secondary controller, which takes over as the new primary storage controller. Takeover on VMware typically occurs within 20 seconds or less. On AWS, it can take up to 30 seconds, due to the time required for network routing configuration changes to take place. 

In AWS, SNAP HA is applied to SoftNAS storage controllers running in a Virtual Private Cloud (VPC). It is recommended to place each controller into a separate AWS Availability Zone (AZ), which provides the highest degree of underlying hardware infrastructure redundancy and availability. 

SNAP HA has been validated in real-world enterprise customer environments and is proven to handle hundreds of millions of files efficiently and effectively. The use of block replication instead of file replication supports hundreds of millions of files and directories. 

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