is this possible? to basically keep my photo library on an external hard drive, but when am out with my mba to use a secondary library that stays on the Air's ssd? And then photostream would sync all the recent stuff, but i'd just clear out the local hard drive every now and then and photostream would automatically sync up with (both libraries, including) my main photo library on the external? let me know if this doesn't make sense. it seems like it would be nice for solid state drives to have some temporary libraries for files that automatically sync up when connected to their local external hard drive, but would this be a workaround for iphoto? otherwise i might just switch to picasa.