Sometimes LUNs are not visible in vCenter or in your vSphere hosts or you are unable to connect to the SAN. You can use the following tips in such situations:
Always verify the settings in your SAN that is publishing the LUN.
Make sure LUNs exist on the same storage network where your vSphere hosts can reach.
LUNs should be readable and writeable by your vSphere hosts.
As previously described, Host ID on the LUN should be less than 1,023 in vSphere hosts 6.0, and less than 255 in vSphere hosts 5.0. The vSphere hosts will not be able to scan higher LUN IDs even if they exist on the SAN.
Make sure the LUNs are configured correctly in your SAN as well as in the vSphere hosts.
From vSphere hosts, verify the LUN information using the VCLI
esxcli storage core path listcommand andr vicfg-mpath –lcommand from the vMA appliance.
Latency is a well-known problem that can occur if your vSphere infrastructure is not set up correctly. As described in previous chapters, use esxtop...