Citrix Provisioning Services reviewed

CentralizedManagement

Article from ADMIN 04/2011

By Timo Dreger

If you manage many identical computers on a server farm, you don't want to patch every single machine separately just to install a security update. Citrix Provisioning Services 5.0 offers a convenient alternative.

The key idea behind Citrix Provisioning Services [1] is to stream a single disk image to a group of servers. Thus, you can centrally update or patch the image, and all servers will receive the changes without having to manage them individually. This image also defines the role played by the server. If you deploy a web server image, the machine becomes a web server; if you transfer a database server image, you add a database server, and so on.

You can distribute standardized desktops in the same way, thus supporting dynamic load balancing, wherein each server on a farm can replace its entire application stack after a simple reboot. Because the hardware is no longer rigidly linked to a specific function, which it alone is capable of executing, the whole setup needs fewer machines. Servers deployed in this way do not need local disks, except for caching. One side effect is that you can restore every single machine to a defined, safe state simply by reloading the image.

Feature Overview

To establish a streaming service of this kind, you'll need a snapshot of a sample installation with the operating system and application stack (golden master). The snapshot is stored on a virtual disk, which Citrix calls a vDisk. vDisks can reside on a provisioning server, file server, or storage network (iSCSI, SAN, NAS, CIFS).

Computers that receive and use the image are target devices in streaming services terminology. They need to be configured to boot off the network and communicate with a provisioning server, from which they load a boot file that specifies where the vDisk intended for them is located and which they then mount for the remainder of the boot process. The target device accesses the vDisk like a local disk and loads the required data from it as needed. This approach requires less network bandwidth than transferring the entire image

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