VSAN-Troubleshooting-Reference-Manual

Diagnostics and Troubleshooting Reference Manual – Virtual SAN
Flash Cache SSD is pulled unexpectedly from ESXi host
When an SSD (acting as the cache tier) is pulled without decommissioning it, all the
Virtual SAN components residing in that disk group go ABSENT and are inaccessible.
In other words, if the flash tier SSD is removed, it will appear as a removal of the
flash device as well as all associated magnetic disks (in hybrid configurations) or
flash devices (in all-flash configurations) providing backing capacity.
Expected behaviors:
If the VM has a policy that includes NumberOfFailuresToTolerate=1 or greater,
the VM’s objects will still be accessible.
Disk group and the disks under the disk group states will be marked as
ABSENT and can be verified via the vSphere web client UI.
All in-flight I/O is halted while Virtual SAN reevaluates the availability of the
objects without the failed component(s) as part of the active set of
components.
If Virtual SAN concludes that the object is still available (based on available
full mirror copy and witness/votes), all in-flight I/O is restarted.
All components residing in this disk group will be marked as ABSENT in the
UI.
The typical time from physical removal of the drive, Virtual SAN processing
this event, marking the component ABSENT halting and restoring I/O flow is
approximately 5-7 seconds.
When the same SSD is placed back on the same host within 60 minutes, no
new objects will be re-built.
When the timeout expires (default 60 minutes), components on the impacted
disk group will be rebuilt elsewhere in the cluster, if capacity is available.
If the VM Storage Policy has NumberOfFailuresToTolerate=0, the VMDK will
be inaccessible if one of the VMDK components (think one component of a
stripe or a full mirror) exists on disk group whom the pulled flash tier SSD
belongs to. To restore the VMDK, the same SSD has to be placed back in the
ESXi host. There is no option to recover the VMDK.
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