I have cca 25 databases which I need to consolidate into 1 database. First I tried to build a ssis package which would copy all data from each table into one place but then
I found a solution and the problem was in SQL Server - it was consuming too much of memory. By default max server memory was set to 2147483647 (this is default value). Since my server has 4gb RAM, I limited this number to 1100 mb. Since then, there were no memory problems, but still, my flow tasks were very slow. The problem was in using Lookup. By default, Lookup selects everything from Lookup table - I changed this and selected only columns I need for lookup - it fastened the process several times.
Now the whole process of consolidation takes about 1:15h.