I ran into the same issue yesterday.
HP DL380 Gen 8
ESXi 5.1 (HP Image Apr 2013, VAAI included)
HP P2000 G3 (Firmware TS240)
After upgrading the host to ESXi 5.5.0 U1 (HP Image Mar 2014), host can't see existing VMFS 5.58 datastores on P2000. Googling around, I found the following:
The workaround is to install the HP P2000 Software Plug-in for VMware VAAI.
https://h20566.www2.hp.com/portal/site/hpsc/template.PAGE/public/psi/swdDetails/?spf_p.tpst=swdMain&...
The solution is to do a firmware update on the P2000 G3. HP released TS251R004 with native VAAI support (T10-compliance for VAAI). The VAAI plug-in is no longer required. I just flashed mine to TS251P002. Host sees everything after reboot.
Hope it helps.
