My SSD is too small to contain both the LR Catalogue and the previews file because I have 200K images and the Previews.lrdata is 700GB. To improve overall performance I have moved everything in the LR Catlg folder to the SSD except the previews file and placed the Previews on a separate drive which I called Areca-T2. To trick LR into using the Previews.lrdata on Areca-T2 a symbolic line file is used to refer all applications including finder to the actual location on Areca-T2.
To create the symbolic location, a ln unix command is used to place a symbolic link in the location that the previews.lrdata file would typically reside, forwarding it to the actual previews file on drive Areca-T2.
The basic format is: ln -s “path to previews file” “phsical file location of Catalogue/Previews.lrdata”
Note that moving the actual file on Areca-T2 or the symbolic link will break the link and it must be re-established.
Open a Terminal window and enter the following command:
ln -s /Volumes/Areca-T2/LR\ Previews\ Sym\ Link/LR\ 7\ JG\ Catalog\ Previews.lrdata /Users/jeffg/LR\ 7\ JG_Catalog/LR\ 7\ JG\ Catalog\ Previews.lrdata