In the 3.6.0 Server Installer, by default the installer makes a backup of the /site and /data folders so that if something goes wrong the customer can recover. However, with larger installations, the /data/executions folder can be many GBs, and this therefore causes the upgrade to spend a long time copying files, and poses the threat of failing due to lack of disk space.
As a workaround, we recommend that upgrading customers take the following precautions:
> Moving the /data/executions folder out of the /data folder but within the same drive
> Then running the upgrade - this will prevent all the temp data being copied into a backup
> Then post install, move it back - this will give you access to your temp data post install