This is an old problem seen in a stress test: b:0:pho> ps pid ppid pgrp uid state wmesg wchan cmd 74743 2616 74743 0 Ds newbuf 0xffffffff81a12af8 sshd 74742 74740 2247 0 DV newbuf 0xffffffff81a12af8 sh 74740 2247 2247 0 D ppwait 0xfffff8013bf5ca20 sh 74739 74737 2779 0 DE newbuf 0xffffffff81a12af8 sed 74737 74736 2779 0 S wait 0xfffff80d806aa530 sh 74736 2789 2779 0 S piperd 0xfffff802250bdbe0 sh 74733 2789 2779 0 DE newbuf 0xffffffff81a12af8 vmstat 68310 41506 2706 0 D+ biowr 0xfffffe00020ebf78 newfs4 68309 41506 2706 0 D+ biowr 0xfffffe00022ca838 newfs4 68308 41506 2706 0 D+ biowr 0xfffffe0001543890 newfs4 68300 0 0 0 DL newbuf 0xffffffff81a12af8 [md10] https://people.freebsd.org/~pho/stress/log/newfs4-3.txt https://people.freebsd.org/~pho/kernel+core.26.flix1.r344492.txz