Solution : https://service.sap.com/sap/support/notes/1303814 (SAP Service marketplace login required)
Key words : 
low-data-volume scenarios, measured trex performance losses, virtual server environments arise, trex-supported operating system, trex performance issues, sap netweaver trex 7, published sizing rules, operating systems supported, high-load environments, virtual machine correctly
Related Notes : 
       
| 1492000 | General Support Statement for Virtual Environments | 
| 1249465 | TREX 7.1: Installing TREX for Embedded Search | 
| 1164979 | SAP NetWeaver 7.0 Embedded Search: Central Note | 
| 1122387 | Linux: SAP Support in virtualized environments | 
| 1094413 | Applications based on SAP NetWeaver 7.0 using TREX 7.1 | 
| 1003900 | TREX 7.1: Central note | 
| 965097 | TREX 7.1 platforms |