Citrix Systems 6.2.0 manual VM Block Devices

3.4.1. VM Block Devices

In the para-virtualized (PV) Linux case, block devices are passed through as PV devices. XenServer does not attempt to emulate SCSI or IDE, but instead provides a more suitable interface in the virtual environment in the form of xvd* devices. It is also sometimes possible (depending on the OS) to get an sd* device using the same mechanism, where the PV driver inside the VM takes over the SCSI device namespace. This is not desirable so it is best to use xvd* where possible for PV guests (this is the default for Debian and RHEL).

For Windows or other fully virtualized guests, XenServer emulates an IDE bus in the form of an hd* device. When using Windows, installing the XenServer Tools installs a special PV driver that works in a similar way to Linux, except in a fully virtualized environment.

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