Thanks, I have done some testing and using 1 disk on Centos6, I get 250-270Mbyte/s, using 2 disk in raid1 or not I get only 125-127Mbyte/s, sometimes 160Mybte/s (using: hdparm -t /dev/sda and /dev/md0)
I think there my be a problem somewhere, since 125Mbytes sounds like SATA1 1,5Gbps. Maybe the disk is faster at the beginning of the disk, maybe there is a limitation when using more than 1 virtual disk.
The disks are sata3 and I'm using the grey sata connector that are too sata3 (6Gbps)
Another point is that Veeam Free does not work with ESXi Free, it says on the download page:
Note: Free ESXi is not supported.
Having a good backup is critical, but I don't think I can work without RAID1, even if it is slower. I know the best option is to have a hardware raid from a supported ESXi hardware vendor, so I will keep weighting my options.