We experienced some strange thing in our mongodb gridfs platform. The platform actually is a bi Xeon E5 (bi quad core) with 128GB of memory, running on freebsd 9 with a zfs pool dedicated for mongodb. [root@mongofile1 ~]# uname -sr FreeBSD 9.1-RELEASE our /boot/loader.conf vfs.zfs.arc_min="2048M" vfs.zfs.arc_max="7680M" vm.kmem_size_max="16G" vm.kmem_size="12G" vfs.zfs.prefetch_disable="1" kern.ipc.nmbclusters="32768" /etc/sysctl.conf net.inet.tcp.msl=15000 net.inet.tcp.keepidle=300000 kern.ipc.nmbclusters=32768 kern.ipc.maxsockbuf=2097152 kern.ipc.somaxconn=8192 kern.maxfiles=65536 kern.maxfilesperproc=32768 net.inet.tcp.delayed_ack=0 net.inet.tcp.sendspace=65535 net.inet.udp.recvspace=65535 net.inet.udp.maxdgram=57344 net.local.stream.recvspace=65535 net.local.stream.sendspace=65535 we follow the recommendation for the ulimit : [root@mongofile1 ~]# su - mongodb $ ulimit -a cpu time (seconds, -t) unlimited file size (512-blocks, -f) unlimited data seg size (kbytes, -d) 33554432 stack size (kbytes, -s) 524288 core file size (512-blocks, -c) unlimited max memory size (kbytes, -m) unlimited locked memory (kbytes, -l) unlimited max user processes (-u) 5547 open files (-n) 32768 virtual mem size (kbytes, -v) unlimited swap limit (kbytes, -w) unlimited sbsize (bytes, -b) unlimited pseudo-terminals (-p) unlimited This server have a twin (same config exactly) for ReplSet in other data center and we have a virtualized arbiter. Some time, almost 3 days, the process of mongodb exit. The problem begin with: Fri Nov 8 11:27:31.741 [conn774697] end connection 192.168.10.162:47963 (23 connections now open) Fri Nov 8 11:27:31.770 [initandlisten] can't create new thread, closing connection Fri Nov 8 11:27:31.771 [rsHealthPoll] replSet member mongofile2:27017 is now in state DOWN Fri Nov 8 11:27:31.774 [initandlisten] connection accepted from 192.168.10.162:47968 #774702 (20 connections now open) Fri Nov 8 11:27:31.774 [initandlisten] connection accepted from 192.168.10.161:28522 #774703 (21 connections now open) Fri Nov 8 11:27:31.774 [initandlisten] connection accepted from 192.168.10.164:15406 #774704 (22 connections now open) Fri Nov 8 11:27:31.774 [initandlisten] connection accepted from 192.168.10.163:25750 #774705 (23 connections now open) Fri Nov 8 11:27:31.810 [initandlisten] connection accepted from 192.168.10.182:20779 #774706 (24 connections now open) Fri Nov 8 11:27:31.855 [initandlisten] connection accepted from 192.168.10.161:28524 #774707 (25 connections now open) Fri Nov 8 11:27:31.869 [initandlisten] connection accepted from 192.168.10.182:20786 #774708 (26 connections now open) and after many "can create new thread" [root@mongofile1 /usr/mongodb]# tail -n 15000 mongod.log.old |grep "create new thread"|wc 5020 55220 421680 and finish by a magnificent Fri Nov 8 11:30:22.333 [rsMgr] replSet warning caught unexpected exception in electSelf() pure virtual method called Fri Nov 8 11:30:22.333 Got signal: 6 (Abort trap: 6). Fri Nov 8 11:30:22.337 Backtrace: 0x599efc 0x8035cb516 0x599efc <_ZN5mongo10abruptQuitEi+988> at /usr/local/bin/mongod 0x8035cb516 <_pthread_sigmask+918> at /lib/libthr.so.3 Extract of mongodb from top 78126 mongodb 77 20 0 1253G 1449M sbwait 0 0:20 0.00% mongod If I restart the process when it crash, the problem is fixed for almost 3 days. Has anyone seen this before, or know of a fix?