I have setups where I use gvinum to divide a partition or raw disk into smaller concat devices under /dev/gvinum, that i subsequently use hast on to replicate their contents to a central zfs server for backup purposes.

The hast devices get a filesystem, and each contains a single jail.

I have observed this issue on a wide range of hardware and FreeBSD versions (ever since 8.0 or earlier).

When there is heavy I/O on those volumes, the system that has the primary simply freezes. The secondary shows no issues.

In my production environment the secondary is running on top of zfs, but I have observed this in a simple setup where both primary and secondary are on top of gvinum as well.

How-To-Repeat: 1. Create a VM
==============

Created a 8GB dynamically allocated disk and set up a VM with all default settings and two network interfaces: the first interface is bridged to my LAN and assigned by dhcp and the second is an internal network.

Install FreeBSD 8.4 from disc1 iso. 

Use the entire 8GB disk to create a slice, and install these partitions:

# /dev/ad0s1:
8 partitions:
#          size     offset    fstype   [fsize bsize bps/cpg]
  a:    1466368          0    4.2BSD        0     0     0
  b:     880600    1466368      swap
  c:   16777089          0    unused        0     0     # "raw" part, don't edit
  d:    1048576    2346968    4.2BSD        0     0     0
  e:    1048576    3395544    4.2BSD        0     0     0
  f:    8333312    4444120    4.2BSD        0     0     0
  g:    3999657   12777432    4.2BSD        0     0     0

ad0s1g will be the gvinum partition, the fstab is as follows:

# Device                Mountpoint      FStype  Options         Dump    Pass#
/dev/ad0s1b             none            swap    sw              0       0
/dev/ad0s1a             /               ufs     rw              1       1
/dev/ad0s1e             /tmp            ufs     rw              2       2
/dev/ad0s1f             /usr            ufs     rw              2       2
/dev/ad0s1d             /var            ufs     rw              2       2
/dev/acd0               /cdrom          cd9660  ro,noauto       0       0


The /etc/rc.conf of this vm is:

# Created: Fri May  9 20:21:48 2014
# Enable network daemons for user convenience.
# Please make all changes to this file, not to /etc/defaults/rc.conf.
# This file now contains just the overrides from /etc/defaults/rc.conf.
hostname="hosta"
ifconfig_em0="dhcp"
ifconfig_em1="inet 192.168.13.1 netmask 255.255.255.0"

The /etc/hosts is:

::1                     localhost localhost.my.domain
127.0.0.1               localhost localhost.my.domain
192.168.13.1            hosta
192.168.13.2            hostb

I then pulled the source from svn and compiled the kernel and world:

# cd /usr
# svn checkout https://svn.eu0.freebsd.org/base/release/8.4.0 src
# cd src
# make buildkernel && make installkernel
# make installkernel
# mergemaster -p -iFU
# make installworld
# mergemaster -iFU
# reboot

Then set up gvinum with 'gvinum create' and the following config:

drive store device /dev/ad0s1g
volume demo
plex name demo.p0 org concat vol demo
sd name demo.p0.s0 drive store len 2097152s driveoffset 265s plex demo.p0 plexoffset 0s

Finally, install bonnie (pkg_add -r bonnie).

2. Clone the VM
===============

Cloned the VM to create hostb, with rc.conf modified as such:

# Created: Fri May  9 20:21:48 2014
# Enable network daemons for user convenience.
# Please make all changes to this file, not to /etc/defaults/rc.conf.
# This file now contains just the overrides from /etc/defaults/rc.conf.
hostname="hostb"
ifconfig_em0="dhcp"
ifconfig_em1="inet 192.168.13.2 netmask 255.255.255.0"

3. Configure hastd
==================

Created /etc/hast.conf on both vm's as follows;

resource demo {
        on hosta {
                remote 192.168.13.2
                local /dev/gvinum/demo
        }
        on hostb {
                remote 192.168.13.1
                local /dev/gvinum/demo
        }
}

Start & init hast on hosta:

root@hosta# /etc/rc.d/hastd onestart
root@hosta# hastctl create demo
root@hosta# hastctl role primary demo
root@hosta# newfs -U /dev/hast/demo

and on hostb:

root@hostb# /etc/rc.d/hastd onestart
root@hostb# hastctl create demo
root@hostb# hastctl role secondary demo

4. Mount and start bonnie
=========================

root@hosta# mkdir /mnt/demo
root@hosta# mount /dev/hast/demo /mnt/demo
root@hosta# cd /mnt/demo
root@hosta# bonnie & bonnie & bonnie & bonnie &

Wait till the system freezes.

I normally have gstat running on another pty, but that shouldn't make a difference.