True or False: Always use Provisioning Services

Test your Citrix muscle…

True or False: Always use Provisioning Services

Answer: False

There has always been this aura around Machine Creation Services in that it could not hold a candle to Provisioning Services; that you would be completely insane to implement this feature in any but the simplest/smallest deployments.

How did we get to this myth? Back in March of 2011 I blogged about deciding between MCS and PVS. I wanted to help people decide between using Provisioning Services and the newly released Machine Creation Services. Back in 2011, MCS an alternative to PVS in that MCS was easy to setup, but had some limitations when compared to PVS. My blog and decision tree were used to help steer people into the PVS route except for the use cases where MCS made sense.

Two and a half years passed and over that time, MCS has grown up. Unfortunately, I got very busy and didn’t keep this decision matrix updated. I blame the XenDesktop product group. How dare they improve our products. Don’t they know this causes me more work? 🙂

It’s time to make some updates based on improvements of XenDesktop 7 (and these improvements aren’t just on the MCS side but also on the PVS side as well).

So let’s break it down:

  • Hosted VDI desktops only: MCS in XenDesktop 7 now supports XenApp hosts. This is really cool, and am very happy about this improvement as so many organizations understand that XA plays a huge part in any successful VDI project.
  • Dedicated Desktops: Before PVD, I was no fan of doing dedicated VDI desktops with PVS. With PVD, PVS dedicated desktops is now much more feasible, like it always was with MCS
  • Boot/Logon Storms: PVS, if configured correctly, would cache many of the reads into system memory, helping to reduce the Read IOPS. Hypervisors have improved over the past 2 years to help us with the large number of Read disk operations. This helps lessen the impact of the boot/logon storms when using MCS.
  • SAN Required: MCS doesn’t require a SAN. This is a long-held misconception mostly because MCS was so new and unknown. I’ve seen many go with local storage when using MCS.
  • Change control: This one was just a little confusing and I was never happy with how I dealt with it. Basically, it used to be difficult to manage PVS images and the entire process behind it. PVS has improved over the years to make this much easier and streamlined with automated tools.

That’s much better. But wait, there is still one item not crossed out yet.

  • Blade PCs: Yes, MCS only works on top of a hypervisor. So if you go with a blade PC or a physical target, you still use PVS. This is a great option for labs and classrooms.

So what is one supposed to use if they don’t need blade PCs or physical targets? My thoughts…

  • If you already use PVS, then keep using PVS
  • If you are new and you have enough storage throughput to support slightly higher IOPS requirements from MCS, use MCS due to simplicity

In a future blog, we will dive a little deeper into the technical impact both of these options will have including IOPS, storage space and resource requirements.

NOTE: This blog is about XenDesktop 7 and MCS/PVS.  Older and newer version have different features/functionality. 

Daniel – Lead Architect


True or False: Citrix Provisioning Services requires PXE

Test your Citrix knowledge…

True or False: Citrix Provisioning Services requires PXE

Answer: False

When using Provisioning Services, which is an optional component of XenDesktop, the target device utilizes a bootstrap file, which initializes the Provisioning Services stream. The target device must be able to obtain that bootstrap file, or else the stream will never begin.

Unfortunately, I still hear people saying that the only way to accomplish this is with PXE, which is incorrect.

Provisioning Services has a few different options for delivering the bootstrap file (these have been the most common approaches for many years):

  1. The DHCP Method:
    Target device boots and sends DHCP discover broadcast
    DHCP server responds with a client IP, Option 66 & 67
    Target device uses the IP and contacts the server identified in Option 66 requesting the file from option 67.
    The PVS server sends the requests bootstrap file via TFTP to the target device.
  2. The PXE Method:
    Target device boots and sends DHCP discover broadcast with Option 60 PXE Client
    DHCP server responds with IP
    PVS Servers, which are running PXE Services, respond with Boot Server
    Client uses the IP and picks one of the PVS responses and requests more information
    PVS responds with boot server/file name information
    Target device contacts the boot server and requests the file name.
    The PVS server sends the requests bootstrap file via TFTP to the target device.
  3. The Local Method: An local file is created with the Boot Device Manager, a component of Provisioning Services. The local file is the bootstrap file, which tells the target how to contact the Provisioning Services farm. It is assigned to each target device either as an ISO attached to the target deices DVD drive, a USB drive, or as a small attached virtual hard disk drive.

It is a pretty good mix of organizations opting for DHCP or Local, much less using the PXE method. Both work, but DHCP and PXE requires more integration with your current environment than the Local method.

Daniel – Lead Architect