We do a disk-to-disk copy of the directory containing our Unicorn data starting at 10 PM Saturday while the system is running. Copying of 35 GB takes us 6 hours. We do a halt of Unicorn at 4AM Sunday, then use the Unix find command to identify files which have been modified since backup was begun:
find $subdirectory -type f -newer $timestamp.file >> $recopy.list
We reserve the 5AM-8AM Sunday time slot for AIX & hardware maintenance and keep Unicorn halted whether maintenance is required or not. We also reserve the right to halt Unicorn 5-7 AM Thursday and 5-8 AM Saturday.