Time used to convert a TB sized ext3 filesystem to btrfs

I have expanded my 11×1.5TB RAID6 to 10X3TB, and since i have everything in one ext3-filsystem, i realised that ext3 simply do not support such filesystem sizes yet. Or to be correct, the filesystem supports it but it is still not possible to resize a filsystem on Ubuntu above 16TB.

I could only find to solution which did not force me to drop all data, and that was to convert it to btrfs, as it support a convertion. I did not time the whole process but it did take me less than 30 hours for 9.5 TB.