Cannot add VMFS datastore to ESXi host (only gives option to format a new drive)


Hello all,

I have an issue with 1 FC LUN that can be seen as a device through multiple paths on all 10 hosts in a cluster but it only appear as a VMFS datastore on 6 of the hosts. Other LUNs from the same array appear fine on all hosts. All 10 hosts see the LUN with the same LUN ID and all hosts are identical with respect to ESXi version (5.0 Update 2), HBA models and firmware.

On the 4 hosts that can see the device but not the VMFS datastore it appears that it sees the LUN as a snapshot: “esxcli storage vmfs snapshot list” results in:

Volume Name: LUN101_SAS2
VMFS UUID: 4f5e5cbb-a87cd2c6-86e9-d8d385f98034
Can mount: true
Reason for un-mountability:
Can resignature: false
Reason for non-resignaturability: the volume is being actively used
Unresolved Extent Count: 1

The above VMFS UUID matches the VMFS UUID seen on the 6 hosts that can see the VMFS datastore.

When I try to use “Add Storage”, the device appears with a VMFS Label of: LUN101_SAS2(head). I’m not sure why (head) has been appended to the VMFS label. On the following screen the “Keep existing signature” and “Assign a new signature” options are greyed out. The only option is “Format the disk”. I need to keep the existing signature as there are running VMs that have their .vmx and .vmdk files on this LUN.

Would the fact that I have running VMs on this LUN be preventing me from choosing the “Keep existing signature” option?

Will I need to Storage vMotion these VMs to another LUN before I can add the VMFS datastore to the 4 hosts?


Try the following command

#esxcfg-volume -l

This ought to show the volume

To persistently mount the volume, use esxcfg-volume -M followed by either the UUID or the name of the volume. So for the example above it would be

esxcfg-volume -M 4f5e5cbb-a87cd2c6-86e9-d8d385f98034



2 thoughts on “Cannot add VMFS datastore to ESXi host (only gives option to format a new drive)

  1. Pingback: Adding iSCSI storage to ESXi host | Andrew's blog of things

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