When a magnetic disk or flash capacity device fails, vSAN evaluates the accessibility of the objects on the device and rebuilds them on another host if space is available and the Primary level of failures to tolerate is set to 1 or more.
Component Failure State and Accessibility
The vSAN components that reside on the magnetic disk or flash capacity device are marked as degraded.
Behavior of vSAN
vSAN responds to the capacity device failure in the following ways.
| Parameter | Behavior |
|---|---|
| Primary level of failures to tolerate | If the Primary level of failures to tolerate in the VM storage policy is equal to or greater than 1, the virtual machine objects are still accessible from another ESXi host in the cluster. If resources are available, vSAN starts an automatic reprotection. If the Primary level of failures to tolerate is set to 0, a virtual machine object is inaccessible if one of the object's components resides on the failed capacity device. Restore the virtual machine from a backup. |
| I/O operations on the capacity device | vSAN stops all running I/O operations for 5-7 seconds until it re-evaluates whether an object is still available without the failed component. If vSAN determines that the object is available, all running I/O operations are resumed. |
| Rebuilding data | vSAN examines whether the hosts and the capacity devices can satisfy the requirements for space and placement rules for the objects on the failed device or disk group. If such a host with capacity is available, vSAN starts the recovery process immediately because the components are marked as degraded. If resources are available, an automatic reprotect will occur. |
