UPDATE: VMware released a patch for this issue. See my post here for more info.
<update>VMware released KB2076392 ‘Frequent NFS APDs after upgrading ESXi to 5.5 U1 (2076392)‘
On Twitter Nick Howell, a NetApp employee , warns VMware vSphere 5.5 customers not to upgrade to ESXi 5.5 Update 1. Because of a vSphere issue NFS disconnects are likely to happen.
This issue seems to occur with any NFS storage vendor, not just NetApp.
For NetApp customers the issue seems to occur when using Data ONTAP 8.0 7-Mode. Netapp is investigating if this isuse occors on cDOT as well.
According to Nick Howell, vSphere 5.5 Update 1 is not yet added to the NetApp Interoperability Matrix Tool which is a web-based utility. It enables you to search for information about the configurations for NetApp products that work with third-party products and components that meet the standards and requirements specified by NetApp.
Nothing more is known at the moment which can be shared externally. VMware and NetApp are aware of the issue.
VMware published a Knowledgebase article on this issue. The workaround is to use vSphere 5.5 GA
The error related to vSphere 5.5 Update 1 NFS shown in vCenter Server could be:
Device or filesystem with identifier <xxx> has entered the All Paths Down state.
The error is shown here.
Other bloggers reported as well on this issue.
Michael Webster: Heads Up Alert: vSphere 5.5 U1 NFS Random Disconnection Bug!
Nick Howell (who posted this alert first on Twitter) NFS Disconnects in VMware vSphere 5.5 U1
Duncan Epping Alert: vSphere 5.5 U1 and NFS issue!
There are other NetApp NFS connectivity issues on vSphere as described in this KB. This issue is related to MaxQueueDepth. datacenterdan.com has more info on this.
some issues reported on Twitter