13 August 2012 Jarret Lavallee

Recently I saw a customer that had trouble vMotioning VMs on NFS datastores. This was occurring on multiple hosts across multiple datastores. It turns out that the customer had mounted some datastores as Read-only on a few hosts. Unfortunately its not straight forward to check for Read-only status on the command line, so I put it up here.

The first thing to try is to create a new file on the datastore

\# touch /vmfs/volumes/ISOs/deleteme  
touch: /vmfs/volumes/ISOs/deleteme: Read-only file system  

Creating a new file failed with a Read-only file system error. This could mean that it was mounted as read only or the export does not include write permissions. I went to check the mount using esxcfg-nas command. Unfortunately it does not tell us much.

\# esxcfg-nas -l  
ISOs is /data/files/ISOs from fileserver2 mounted available  

We can check more mount properties by using esxcli (5.x)

esxcli storage nfs list  
Volume Name Host Share Accessible Mounted Hardware Acceleration  
\---\---\---\-- -\---\---\---\- --\---\---\---\---\-- -\---\---\--- \---\---\- --\---\---\---\---\---\----  
ISOs fileserver2 /data/files/ISOs true true Not Supported  

Still it did not tell us if it was mounted Read-only. Let’s check the mount properties in the esx.conf

\# cat /etc/vmware/esx.conf |grep ISOs  
/nas/ISOs/enabled = "true"  
/nas/ISOs/host = "fileserver2"  
/nas/ISOs/readOnly = "true"  
/nas/ISOs/share = "/data/files/ISOs"  

Finally we see that it is mounted Read-only. So it makes sense that we could not vMotion a VM to it.

Another way to check this is using vsish.

\# vsish -e cat /vmkModules/nfsclient/mnt/ISOs/properties |grep readOnly  

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