Block storage over a network.
WHAT IT IS
Storage presented as block devices, as though locally attached.
WHAT THAT MEANS
The client creates its own file system on it.
WHAT PROTOCOLS ARE USED
Fibre channel, on dedicated infrastructure Block protocol over standard networks Newer protocols designed for very low latency over networks
WHAT IT SUITS
Databases Virtualisation, where hosts share storage Anything requiring block-level access and low latency
WHAT SHARED STORAGE ENABLES IN VIRTUALISATION
Moving running machines between hosts, and restarting them elsewhere on host failure.
WHY THAT IS THE MAIN REASON IT EXISTS IN MANY DEPLOYMENTS
Without it, a host failure means its machines are unavailable until restored.
WHAT MULTIPATHING PROVIDES
Several paths to the same storage, surviving a path failure.
WHAT TO CONFIGURE
Multipathing, correctly, which is frequently overlooked.
WHAT HAPPENS WITHOUT IT
A single cable or switch failure disconnects storage, and machines fail.
WHAT TO SEPARATE
Storage traffic from general network traffic.
WHY
Storage is latency-sensitive and congestion causes timeouts that look like drive failures.
WHAT TO MONITOR
Latency, path status, and capacity.
