Hi all, we run a > 500 TiB backup system on iSCSI targets using 19 BTRFS filesystems (the biggest of which is 110 TiB) on Ubuntu 14.04 LTS and various kernel versions. Btrfs-Progs v3.17.1. The hardware is a 24 core Xeon E5-2620 on an Intel S2600GZ board with 128 GiB RAM. Since btrfs has changed to kworkers (I think in 3.15) the frontend server somewhat randomly crashes with soft lockups (see attachment). The system is rock solid with the 3.14.22 kernel. The lockups happen during the nightly cron-controlled rsync backups and occur at random times during this process. We are totally aware of the fact that this tends to be one of those “it doesn’t work” bug reports, but it’s really hard to pin down the source of the problem other than it seems to be related to the kworkers. We’d love to provide any feedback we can, please let us know what you need. Regards Patrick -- Patrick Schmid support: +41 44 633 2668 IT Services Group, HPT H 8 voice: +41 44 633 3997 Departement Physik, ETH Zurich CH-8093 Zurich, Switzerland