This article is intended for administrators considering either a 2x node or a 3x node SvSAN architecture
SvSAN is a software defined storage solution that presents synchronously mirrored MPIO disks over iSCSI. Thanks to its witness technology this enables the solution to eliminate any “single point of failure” starting with just 2 nodes. With the density of compute, memory and storage achievable in today’s servers, be they tower, rack, or edge focused, it is possible to build large environments in a pair of servers.
SvSAN utilizes internal RAID, be it hardware RAID adapters or software RAID 1 or 10 provided by
the VSAs, to enable internal node resiliency. This alongside the synchronous mirroring of the
storage enables cross-node resiliency.
Network resiliency is enabled through interface traffic flags, multiple network interfaces that can be failed between and support for direct connect cabling.
SvSAN licenses the consumed, RAIDed storage assigned to the VSA, excluding cache capacity and is able to share to external compute nodes completely free of charge. SvSAN supports the a 2x node hyperconverged configuration
Adding compute nodes with any VMs able to run in compute on any node, vMotion between any node and tolerate any single node down.
A 3-node configuration still leverages 1:1 mirroring, i.e. a replication factor of 2.
With this configuration each of the 3 nodes hosting 10TB of RAIDed storage all 3 nodes would see 3x 5TB mirrored e.g. 15TB total, highly available shared storage volumes to tolerate any single node down.
It is possible to build self-healing clusters by leaving spare capacity in the nodes, in a 3-node, to maintain high availability with a node down.
Watch this video for more information