There are two bugs (in my opinion):
1. It is impossible to create database with secondary file (or add file to existing database) with absolute path to the disk other than c:, i.e 'd:\data2.fdb' - server responds: 'File name is invalid'. In the same environment FB 2.0.3 works perfectly.
2. Option MaxFileSystemCache works only for the first database file.
I set MaxFileSystemCache to 0 and created database with 2 files. And then I inserted many records with big blobs. During writing data to the first file the usage of system memory was ok (stable and not so big, about 40%). When FB used all pages in the first file and started to write to the socondary file the used memory was dramaticaly grew up up to 99% and the system almost stopped to work.