High availability data storage and failovers
High availability is crucial to many applications. Despite using high-quality hardware and superior connection, any node (network, server, storage equipment, etc) is still a subject for crashes due to power shortages, communication and equipment faults, fire incidents, maintenance problems or a human factor, which results in loss of all active connections and data transactions as well as in service termination. In case the provided services are structured so that they aren’t dependent on the availability of a single node, a redundant node (or nodes) should be present. When aware of the original node failure, these redundant nodes could continue serving clients, effectively replacing the missing node.
This process is commonly known as a failover. Naturally, there could be either fully automatic or manual failover, the latter requiring the tech team deployment or administrator’s approval.
Open-E delivers automatic NAS (NFS) failover, based on two nodes of active-passive configuration. You can buy it as Data Storage Software V6 extension.
Failover using NFS (file access) protocol
The block access used in iSCSI is usually faster, more general and universal, supporting virtually any application including:
- exchange servers,
- backups, etc.
But the file access is more structured - it supports ownerships, access restrictions, etc, and it is especially convenient if it needs to share the files between multiple users or user groups with different access policies.
The main difference between block-based iSCSI and file-based NFS protocols are file locks of the latter. So even if messaging layer detects the failure and replicating layer has successfully synchronized both servers at the block-level, there is still a problem of locks opened by the clients. If the exported folder fails over from node one to node two, the lock files will remain on the server originally used to manage them. This causes a problem to NFS: clients start to transmit error messages, and can no longer access the files they require. To avoid this, the lock files also have to migrate to the new server.
If you're a full version of Data Storage Software V6 user you can extend the functionality of this product investing in NAS (NFS) Failover extension.