"NO STORAGE, NO DATACENTER"Well, there is no doubt, the storage is the most important piece of the datacenter. VMware ESXi hypervisor is usually just an I/O storage passthrough component with some additional intelligence like
- native storage multipathing (NMP),
- fair storage I/O scheduling (SIOC),
- I/O filtering (VAIO),
- fixed (FIXED),
- most recently used (aka MRU) and
- round robin (RR).
- Inquiry (Requests general information of the target device)
- Test/Unit/Ready aka TUR (Checks whether the target device is ready for the transfer operation)
- Read (Transfers data from the SCSI target device)
- Write (Transfers data to the SCSI target device)
- Request Sense (Requests the sense data of the last command)
- Read Capacity (Requests the storage capacity information)
- SCSI_HOST_BUS_BUSY 0x02
- SCSI_HOST_SOFT_ERROR 0x0b
- SCSI_HOST_RETRY 0x0c
... storage path does not fail over when the path to the target is up and sending reponse back into the initiator even the LUN is not available for whatever reasons.
What is the advanced option enable_action_OnRetryErrors?
- Khalil, Mostafa : Storage Implementation in vSphere 5.0 (VMware Press)
- Mao Tao (IBM) : Tour the Linux generic SCSI driver
- VMware KB : Storage path does not fail over when TUR command repeatedly returns retry requests (2106770)
- VMware Documentation : No Failover for Storage Path When TUR Command Is Unsuccessful