CTDB cluster. It is just extra node that can be used as a test
client or similar.
+Corrupt system disks
+====================
+
+Recent versions of KVM seem to have fixed problems where the
+combination of qcow2 file format, virtio block devices and writeback
+caching would cause result in corrupt. This means the default system
+disk bus type (a.k.a. SYSTEM_DISK_TYPE) is now virtio.
+
+If using an older version of KVM or if you experience corruption of
+the system disk, try using IDE system disks:
+
+ SYSTEM_DISK_TYPE=ide
+
iSCSI shared disks
==================
Raw IDE system disks
====================
-RHEL versions of KVM do not support the SCSI block device emulation,
-so autocluster now defaults to using an IDE system disk instead of a
-SCSI one. Therefore, you can use virtio or ide system disks.
-However, writeback caching, qcow2 and virtio are incompatible and
-result in I/O corruption. So, you can use either virtio system disks
-without any caching, accepting reduced performance, or you can use IDE
-system disks with writeback caching, with nice performance.
+Older RHEL versions of KVM did not support the SCSI block device
+emulation, and produced corruption when virtio disks were used with
+qcow2 disk images and writeback caching. In this case, you can use
+either virtio system disks without any caching, accepting reduced
+performance, or you can use IDE system disks with writeback caching,
+with nice performance.
For IDE disks, here are the required settings: