What:		/sys/bus/xen-backend/devices/*/devtype
Date:		Feb 2009
KernelVersion:	2.6.38
Contact:	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
                The type of the device.  e.g., one of: 'vbd' (block),
                'vif' (network), or 'vfb' (framebuffer).

What:		/sys/bus/xen-backend/devices/*/nodename
Date:		Feb 2009
KernelVersion:	2.6.38
Contact:	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
                XenStore node (under /local/domain/NNN/) for this
                backend device.

What:		/sys/bus/xen-backend/devices/vbd-*/physical_device
Date:		April 2011
KernelVersion:	3.0
Contact:	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
                The major:minor number (in hexidecimal) of the
                physical device providing the storage for this backend
                block device.

What:		/sys/bus/xen-backend/devices/vbd-*/mode
Date:		April 2011
KernelVersion:	3.0
Contact:	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
                Whether the block device is read-only ('r') or
                read-write ('w').

What:		/sys/bus/xen-backend/devices/vbd-*/statistics/f_req
Date:		April 2011
KernelVersion:	3.0
Contact:	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
                Number of flush requests from the frontend.

What:		/sys/bus/xen-backend/devices/vbd-*/statistics/oo_req
Date:		April 2011
KernelVersion:	3.0
Contact:	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
                Number of requests delayed because the backend was too
                busy processing previous requests.

What:		/sys/bus/xen-backend/devices/vbd-*/statistics/rd_req
Date:		April 2011
KernelVersion:	3.0
Contact:	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
                Number of read requests from the frontend.

What:		/sys/bus/xen-backend/devices/vbd-*/statistics/rd_sect
Date:		April 2011
KernelVersion:	3.0
Contact:	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
                Number of sectors read by the frontend.

What:		/sys/bus/xen-backend/devices/vbd-*/statistics/wr_req
Date:		April 2011
KernelVersion:	3.0
Contact:	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
                Number of write requests from the frontend.

What:		/sys/bus/xen-backend/devices/vbd-*/statistics/wr_sect
Date:		April 2011
KernelVersion:	3.0
Contact:	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
                Number of sectors written by the frontend.

What:           /sys/module/xen_blkback/parameters/max_buffer_pages
Date:           March 2013
KernelVersion:  3.10
Contact:        Roger Pau Monné <roger.pau@citrix.com>
Description:
                Maximum number of free pages to keep in each block
                backend buffer.

What:           /sys/module/xen_blkback/parameters/max_persistent_grants
Date:           March 2013
KernelVersion:  3.10
Contact:        Roger Pau Monné <roger.pau@citrix.com>
Description:
                Maximum number of grants to map persistently in
                blkback. If the frontend tries to use more than
                max_persistent_grants, the LRU kicks in and starts
                removing 5% of max_persistent_grants every 100ms.