Hi all, I'm glad to share that we successfully migrated old 2.x Koha to new one, 3.20. I should also say that this a quite derived version of 3.20, we have added many new features, new modules and changed a lot of codes for the use of public libraries so we may call this Koha version as Koha -- Devinim. We've migrated 1.220.000 active users, 13.700.000 items with active 900 libraries of 1126 public libraries all cities of Turkey. We use 14 servers for all production and 4 servers for test environment. We use MariaDB and Galera Cluster with 4 nodes, 8 apache servers and 1 zebra server. We plan to cluster zebra server in the future, it cannot perform very well for this kind of huge installation. During migration, we also cleaned some dirty data, this was also a big issue for 13m items. We've done many tests before going live. OPAC page is http://koha.ekutuphane.gov.tr Thanks // /Mengü YAZICIOĞLU DEVİNİM Software Consultancy /