I'm working with glusterfs as cinder backend.
when I run instances I can see 2 type of qemu services:
[root@cougar07 ~(keystone_admin)]# nova list
+--------------------------------------+-------+--------+------------+-------------+--------------------------+
| ID | Name | Status | Task State | Power State | Networks |
+--------------------------------------+-------+--------+------------+-------------+--------------------------+
| b2cda446-9ff2-405f-845a-422f5548738f | dafna | ACTIVE | None | Running | novanetwork=192.168.32.2 |
+--------------------------------------+-------+--------+------------+-------------+--------------------------+
[root@cougar07 ~(keystone_admin)]#
[root@cougar07 ~(keystone_admin)]# ps -elf |grep qemu
2 S nova 28760 28700 10 80 0 - 212831 poll_s 18:30 ? 00:00:02 /usr/libexec/qemu-kvm -global virtio-blk-pci.scsi=off -nodefconfig -nodefaults -nographic -machine accel=kvm:tcg -cpu host,+kvmclock -m 500 -no-reboot -kernel /var/tmp/.guestfs-162/kernel.28700 -initrd /var/tmp/.guestfs-162/initrd.28700 -device virtio-scsi-pci,id=scsi -drive file=/var/lib/nova/instances/b2cda446-9ff2-405f-845a-422f5548738f/disk,cache=none,format=qcow2,id=hd0,if=none -device scsi-hd,drive=hd0 -drive file=/var/tmp/.guestfs-162/root.28700,snapshot=on,id=appliance,if=none,cache=unsafe -device scsi-hd,drive=appliance -device virtio-serial -serial stdio -device sga -chardev socket,path=/tmp/libguestfsNphmhH/guestfsd.sock,id=channel0 -device virtserialport,chardev=channel0,name=org.libguestfs.channel.0 -append panic=1 console=ttyS0 udevtimeout=600 no_timer_check acpi=off printk.time=1 cgroup_disable=memory root=/dev/sdb selinux=0 TERM=xterm
6 S qemu 29002 1 65 80 0 - 624337 futex_ 18:30 ? 00:00:09 /usr/libexec/qemu-kvm -name instance-0000004b -S -M rhel6.5.0 -cpu Opteron_G3,+nodeid_msr,+wdt,+skinit,+ibs,+osvw,+3dnowprefetch,+cr8legacy,+extapic,+cmp_legacy,+3dnow,+3dnowext,+pdpe1gb,+fxsr_opt,+mmxext,+ht,+vme -enable-kvm -m 2048 -realtime mlock=off -smp 1,sockets=1,cores=1,threads=1 -uuid b2cda446-9ff2-405f-845a-422f5548738f -smbios type=1,manufacturer=Red Hat Inc.,product=OpenStack Nova,version=2013.2-0.25.rc1.el6ost,serial=44454c4c-4a00-1044-804c-b5c04f39354a,uuid=b2cda446-9ff2-405f-845a-422f5548738f -nodefconfig -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/instance-0000004b.monitor,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc,driftfix=slew -no-kvm-pit-reinjection -no-shutdown -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -drive file=/var/lib/nova/instances/b2cda446-9ff2-405f-845a-422f5548738f/disk,if=none,id=drive-virtio-disk0,format=qcow2,cache=none -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -netdev tap,fd=22,id=hostnet0,vhost=on,vhostfd=23 -device virtio-net-pci,netdev=hostnet0,id=net0,mac=fa:16:3e:b0:3f:49,bus=pci.0,addr=0x3 -chardev file,id=charserial0,path=/var/lib/nova/instances/b2cda446-9ff2-405f-845a-422f5548738f/console.log -device isa-serial,chardev=charserial0,id=serial0 -chardev pty,id=charserial1 -device isa-serial,chardev=charserial1,id=serial1 -device usb-tablet,id=input0 -vnc 10.35.160.135:0 -k en-us -vga cirrus -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x5
0 S root 29022 13613 0 80 0 - 25813 pipe_w 18:30 pts/2 00:00:00 grep qemu
after I delete the instance only one of the services is stopped:
[root@cougar07 ~(keystone_admin)]# nova delete b2cda446-9ff2-405f-845a-422f5548738f
[root@cougar07 ~(keystone_admin)]# nova list
[root@cougar07 ~(keystone_admin)]# ps -elf |grep qemu
2 S nova 28760 28700 3 80 0 - 212831 poll_s 18:30 ? 00:00:02 /usr/libexec/qemu-kvm -global virtio-blk-pci.scsi=off -nodefconfig -nodefaults -nographic -machine accel=kvm:tcg -cpu host,+kvmclock -m 500 -no-reboot -kernel /var/tmp/.guestfs-162/kernel.28700 -initrd /var/tmp/.guestfs-162/initrd.28700 -device virtio-scsi-pci,id=scsi -drive file=/var/lib/nova/instances/b2cda446-9ff2-405f-845a-422f5548738f/disk,cache=none,format=qcow2,id=hd0,if=none -device scsi-hd,drive=hd0 -drive file=/var/tmp/.guestfs-162/root.28700,snapshot=on,id=appliance,if=none,cache=unsafe -device scsi-hd,drive=appliance -device virtio-serial -serial stdio -device sga -chardev socket,path=/tmp/libguestfsNphmhH/guestfsd.sock,id=channel0 -device virtserialport,chardev=channel0,name=org.libguestfs.channel.0 -append panic=1 console=ttyS0 udevtimeout=600 no_timer_check acpi=off printk.time=1 cgroup_disable=memory root=/dev/sdb selinux=0 TERM=xterm
0 S root 29158 13613 0 80 0 - 25814 pipe_w 18:31 pts/2 00:00:00 grep qemu
[root@cougar07 ~(keystone_admin)]#
this seems to happen in glusterfs only.
