How Vmirror Works
Vmirror is designed for easy operation with Xsan-compatible storage. Each Vmirror appliance uses SAN-attached, mirroring engine clusters to provide high availability and continuous data protection while also creating redundant paths between host and storage system. Should outage occur anywhere on one of the data paths, one of two hardware mirroring engines fails over instantly to alternate data path and storage without host interruption --- a key requirement for availability-critical environments like HD video broadcast and video post-production.
Mirroring and failover is managed automatically by Vmirror, which is made transparent to system and storage via built-in SAN virtualization. To connected Xserve host systems, Vmirror-protected RAID appears as an "unbreakable" volume that is impervious to component outages. Data is also mirrored synchronously, ensuring continuous protection of data. No host software or drivers are needed for host systems, simplifying administration and eliminating CPU overhead.
As viewed from the host system over a FC connection, a dual-engine engine Vmirror appliance connects to two sets of Xsan-compatible RAID systems to create a single, active-active storage system. From a physical standpoint, Vmirror-protected RAID arrays can also be placed in different physical locations, providing additional an added benefit of disaster protection. In the unlikely event a storage volume fails, failover from primary to mirrored storage volume proceeds by reading from the alternate data path. Failover is nearly instantaneous and, with appropriately configured systems, happens without video frame drops.
Performance-wise, Vmirror dramatically raises streaming rates by alternately reading from each data path (yellow and blue above). Vmirror reads from both mirrored disk sets and effectively doubles sustained throughput.