The Role of Base Disk in Desktop Groups – XenDesktop 5

January 18, 2011

Citrix


>You may have set up your Xendesktop 5 environment using machine creation services and then may not understand why the desktop group creates its down base disk in storage and what exactly is the role of this disk.

Well here is a nice explanation pulled of citrix forums that explains it very nicely.

Base disk is the disk that the machines created by Machine Creation Services for a catalog (the name of the catalog is the first part of the name) will use as a start point. The additional

machines are created as thin clones off this master disk.

When a snapshot or clone operation is performed in XenServer the original disk is marked as readonly and two read-write nodes are created off it, one for the original machine and one for the clone (or snapshot as the snapshot is just a specialised virtual machine). When the Vm wants to read data from the disk it walks back up the tree (which may be many levels deep) until the data is found. Obviously this introduces a performance hit. So as part for the task of creating a catalog, Machine Creation Services creates a copy of the disk data and flattens the delta tree to a single level so that machines created by machine Creation services only have two places to look, their read-write “personal” disk and the read-only parent disk. As you have seen these disks are quite large and on local LVM disks which are “thick” provisioned they will take the full space allocated to them even if they are largely empty. On an NFS SAN or a local disk that has been converted to ‘ext’ format they only take the space that is being used and grow as required.

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About mohamedridha

A keen IT/Technology enthusiast with passion for media and photography

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