I recently had an issue where my “EMC VSI” tab disappeared in my vSphere Client on my vCenter server.  I went to Home -> Solutions & Applications -> EMC and that button was still there.  I clicked into “Feature Manager” and noticed my “Storage Viewer” plugin was listed as disabled.  I right clicked on it and selected Enable but was presented with the following error:

“Attempting to deserialize an empty stream”

I figured might as well try to upgrade it and see what happens; the versions at the time were in the 5.4 range.  I updated the VSI plugin itself, Storage Viewer and installed NaviCLI (Navisphere command line utilities) so that I could talk to older Clariion devices since this VMware environment is connected to both VNX and CX4 arrays.  After that, the versions reported are (Found in Home -> Solutions & Applications -> EMC -> Feature Manager):

“EMC Virtual Storage Integrator (VSI) for VMware vSphere” 5.6.1.2

“Path Management” 5.4.0.15

“Storage Viewer” 5.6.1.20

“Unified Storage Management” 5.6.1.18

 

Unfortunately the problem did not go away.  It turns out that this is a known issue where the VSI preference files get corrupted.  EMC knows it can occur but does not know what causes it, so the only solution is to delete the files and then everything will work fine.  You’ll find the files, all with a .dat extension, in the directory where your vCenter app stores its preferences.  You can probably find it by doing a search for vSphere4 on your server.  Mine ended up being:

C:\Users\Administrator\AppData\Roaming\EMC\Virtual Storage Integrator\vSphere4\Data

That will obviously vary by Windows install drive, etc.  Here are the files that I had to delete:

Once those were removed, everything went back to normal.