Problem:

  • You are using a XenServer machine that is running kernel somewhere around version 2.6.32
  • You have a guest system like Debian Wheezy (currently testing) that is running kernel 3.0+
  • While rebooting your guest system (VM) you are experiencing disk issues like I/O access, ext4 inconsistency, etc…
  • The disks on guest are not mounting properly or are mounted in read-only mode or fsck has problems checking them

Solution:

In the HOST logs you can see probably:

Apr 10 11:04:14 server kernel: blkfront: xvda: barriers enabled

The problem is that 3.0 kernels are not using barriers anymore and there is a bug connected to that with the host kernel. If you are interested in details, check out Debian bug #637234.

The workaround is to use ‘barriers=0’ while mounting the disks in the guest system, so you correct your /etc/fstab to have:

/dev/xvda1        /        ext4      errors=remount-ro,barrier=0      0     1