Evaluation of multi-cloud computing TMR-based model using a cloud simulator Security of data in cloud computing environment is considered to be critical issue because of the importance and sensitivity of the outsourced data in the cloud, as is the trustworthiness of the cloudservice provider. The failure of cloud services and the danger of malicious insiders in the cloud have received intense awareness by cloud users. The aim of this work is to analyse and evaluate an existing MCDB model (Multi-clouds Databases) that utilizes multi-clouds providers. The model adopted a triple modular redundancy (TMR) technique as well as sequential method to develop data trustworthiness ofcloud system and after that to improve the data security feature. Also, it. incorporated Shamir’s sharing algorithm. The evaluation is done through simulation using cloud computing simulator toolkit.