VMware really did an outstanding job with the availability of vSphere 5.1 information at the new vSphere 5.1 Documentation Center. It offers a wide range of documents in searchable HTML format but also offers all guides in PFD, ePub and mobi format. It even has a link to one downloadable zip file with all the vSphere 5 PDFs you need.
ESXi and vCenter Server 5.1 Product Guides:
- vSphere Installation and Setup
- vSphere Upgrade
- vSphere vCenter Server and Host Management
- vSphere Virtual Machine Administration
- vSphere Host Profiles
- vSphere Networking
- vSphere Storage
- vSphere Security
- vSphere Resource Management
- vSphere Availability
- vSphere Monitoring and Performance
- vSphere Troubleshooting
- vSphere Examples and Scenarios [pdf | epub | mobi]
Zip Archives of ESXi and vCenter Server Documentation
