Comment 19 for bug 401094

I put the content of /backup/duplicity and /duplicity in two different new hard drives and rebooted to empty the 8 GB ram. Then, I tried another incremental backup and got around 6-10 MB/sec. (IMHO) due to the empty ram.
I have 3 qcow2 files with a size of 6.5G, 11G and 8.3G in /backup/duplicity/ among other smaller files . Is it better to convert these huge qcow2 in raw format for the incremental backup? The files in raw format will have the sizes 10G, 20G and 100G.