Thanks for your answer, it's my first time with replication job so I followed this configuration: https://helpcenter.veeam.com/docs/backup/vsphere/replication_scenarios.html?ver=95#onsite
I obtain the best results with this configuration. I tried with two proxies, the source with direct San and destination with hotadd but for the same job it take 2 more minutes.
I m just surprised to see nbd. I though to see at minima hotadd.
28/09/2017 17:05:11 :: Using source proxy VMware Backup Proxy for disk Disque dur 2 [san]
28/09/2017 17:05:11 :: Using target proxy VMware Backup Proxy for disk Disque dur 1 [nbd]
My current bottleneck is "Source". I suppose that my production VM storage cannot provide data transfer any faster.