I know people for whom it took 1 month, as well as people who got it approved after 3 months. Even though these were parents of students in Canada, it took surprisingly long to process.
Best bet is to not apply online, since many online applicants for Abu Dhabi have been complaining how long it has taken. Apply paper-based application through VFS locally, they will forward it to the High commission/embassy themselves. Once you submit your application at VFS, they will proceed to take your bio-metric information as well as digital photos.
Good Luck