As received today from the Synology Development team:

Dear Synology users, An important update for the DiskStation Manager (DSM) 6.1 is released. We suggest users to update your DSM as soon as possible to ensure the integrity of your data. Download the update on your DSM: Control Panel > Update & Restore. An open source issue that’s prone to affect data integrity in rare situations has been identified. Although it only affects a handful of users, users are encouraged to upgrade to the latest DSM 6.1.3 update 4 and conduct RAID scrubbing to avoid running into this issue. The issue may occur only when the following conditions are all met: The server is using RAID 5, RAID 6, RAID F1, or SHR with more than 3 disks. The volume is created on EXT4 file system. The server is running on DSM 6.0.2-8451 and above. If your DiskStation meets the criteria, please conduct the following steps: Upgrade to DSM 6.1.3 update 4 (Download now) Conduct RAID scrubbing. (Learn more) The issue was brought to our attention a few weeks ago when the NAS communities discussed the potential data integrity threat that may occur after a RAID 5 repair. In-house investigation revealed the issue stems from Linux feature known as skip_copy. This open source feature contains a slight design fault that may lead to potential data corruption after a RAID array is repaired from degrade mode. Synology team moved quickly to identify and reproduce the issue, which is resolved in the latest DSM 6.1.3 update. Synology is committed to high standards of data protection and safety. Keeping user information safe has always been our priority. In addition, as a vibrant supporter of Open Source, Synology has reported this issue to the Community. By calling to the attention of the mass community, we seek to join forces with influencers in the field in delivering continuous contribution on data integrity and data protection. Owners with the following models should upgrade their models to the DSM 6.1.3 update 4 as soon as possible:

17 series: RS18017xs+, RS4017xs+, RS3617xs+, RS3617xs, RS3617RPxs, DS3617xs, DS1817+, DS1817, DS1517+, DS1517 16 series: RS18016xs+, RS2416+, RS2416RP+, RS816, DS916+, DS716+II, DS716+, DS416play, DS416slim, DS416j, DS416 15 series: RS815+, RS815RP+, RS815, RC18015xs+, DS3615xs, DS2415+, DS2015xs, DS1815+, DS1515+, DS1515, DS715, DS415+, DS415play 14 series: RS3614xs+, RS3614xs, RS3614RPxs, RS2414+, RS2414RP+, RS814+, RS814RP+, RS814, RS214, DS414slim, DS414j, DS414 13 series: RS10613xs+, RS3413xs+, DS2413+, DS1813+, DS1513+, DS713+, DS413j, DS413 12 series: RS3412xs, RS3412RPxs, RS2212+, RS2212RP+, RS812+, RS812RP+, RS812, DS3612xs, DS1812+, DS1512+, DS712+, DS412+ 11 series: RS3411xs, RS3411RPxs, RS2211+, RS2211RP+, RS411, DS3611xs, DS2411+, DS1511+, DS411+II, DS411+, DS411slim, DS411j, DS411

Sincerely, Synology Development Team