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Though APD and PDL events can be unexpected, there are times when they can be avoided with proper planning. VMware provides a process wherein datastores can be unmounted and then the underlying device detached from the ESXi hosts. At that point, removing the devices on the PowerMax causes no harm. The following sections walk the user through the process.
In the following example, the datastore UNMOUNT_DS seen in Figure 61, is unmounted and the device that is associated with it detached in the vSphere Client. Before proceeding, ensure that:
All these issues must be rectified before proceeding or an error is generated.
UNMOUNT_DS meets all these prerequisites so it can be unmounted. Be sure to record the Network Addressing Authority (NAA) identifier of the device as it is required when the device is detached. From an ESXi host, go to Configure -> Storage -> Storage Devices and locate the disk. Since each host may have a different LUN number, only use the WWN. An example is shown in Figure 62.
Once the datastore is identified, right-click the datastore and choose “Unmount” as shown in Figure 63. The unmount may also be accomplished through the CLI. The command to do an unmount is esxcli storage filesystem unmount from the ESXi shell.
A single screen follows with the unmount wizard which lists the conditions under which the datastore will not unmount. For instance, if a VM is running on the datastore or it is being used as an HA heartbeat it fails. The unmount screen is shown in Figure 64.
VMware checks for violations such as registered VMs. If such a violation exists, the following error in Figure 65 is generated and the unmount fails.
Note: If there are multiple ESXi hosts in the cluster, VMware attempts to unmount the datastore from each host. Only those hosts that are in violation fail the unmount.
For those VMs in violation, unregister the VM or Storage vMotion it to another datastore. Once complete, the result is an inaccessible datastore, as shown in Figure 66.
Once the datastore is unmounted, the underlying device must be detached from the ESXi hosts. Start by recalling the WWN gathered before the unmount (60000970000197601879533030304538). Once the device is identified in the Storage Devices of one of the hosts, select DETACH as in Figure 67.
VMware automatically shows all the ESXi hosts where the device is presented. By default, the top radio button is selected, as shown in Figure 68.
To detach the device from all ESXi hosts, select the second radio button as shown in Figure 69.
Once detached, run a rescan of the ESXi hosts to remove the inactive datastore. The device remains in the device list as detached, shown in Figure 70, until the LUN is unmasked from the host and a second rescan is run.
Removing the masking view on the PowerMax completes the process, safely avoiding APD or PDL.