Yesterday some depatment's network switches firmwares were updated and some network interfaces went dead for a short interval (which is perfectly normal).  Unfortunately, the multipathing subsystem which should have routed iscsi packages through the still working interfaces failed and Linux kernel of ukko001 fileserver remounted /cs/ukko filesystem readonly. Fixing this requires that ukko001 is rebooted. The reboot might take as long as 20 minutes. /cs/ukko, /cs/taatto and /cs/hiit filesystems are not accessible during that time (all attempts to access files will hang until the filesystems come back online).