Virtual desktops are popular in companies, governments, and education. Citrix is the leader in desktop virtualization and its MCS technology can help easily manage massive virtual desktops.
Updated by Nick Zhao on 2023/02/06
Citrix is the leader in desktop virtualization and has the mature technologies PVS and MCS for virtual desktop batch provisioning and management. These technologies can help IT administrators easily manage massive virtual desktops based on one template.
This post will mainly introduce MCS technology. If you also would like to know PVS technology, please refer to another post: what is Citrix PVS technology?
Citrix MCS, Machine Creation Service, is a component of Citrix Virtual Apps and Desktops solution. MCS mode is released with XenDesktop 5.0 and is much younger than PVS mode. However, no matter MCS or PVS, they are just storage technology and MCS is released based on linked clone technology. MCS creates VM via linked clone technology and allocates 2 or 3 disks to every VM.
Master Image: it is the virtual disk created based on the snapshot of the template VM and is read-only, containing the content of the system disk of the template VM.
Differencing Disk: it is used to connect the created VM, containing the change of VM (cache).
Identity Disk: it is a disk of about 16 MB, containing some basic information like machine name, SID, user name and password, etc. This information will be imported to VM when the operating system is booted to make sure VM can be recognized correctly.
Personal vDisk (optional): it stores the data which needs to be saved permanently.
For example, if you create a group of virtual desktops via MCS mode, these virtual desktops will be counted as a directory in Studio and in this directory, the related storage LUN in the underlayer of server virtualization has a Master Image. With the addition of multiple Differencing Disks and Identity Disks, the resource pool is formed. All the VMs in the directory will read the operating system on the Master Image at the same time and then the respective I/O will be written into the mounted Differencing Disks.
MCS mode can help create pool-random desktop and pool-static desktop.
Pool-random desktop is for single use because of the mounted Differencing Disk will be deleted every time the VM is rebooted and a new Differencing Disk will be created and formatted to be mounted to the VM so the I/O written last time will not be saved. On the contrary, the data of pool-static desktop will be saved because the Differencing Disk will not be deleted.
MCS is loved by IT administrators because its simple deployment and usage but there are still some drawbacks of it, like occupying too much storage and too much load to Master Image I/O reading.
MCS can help create the directory and allocate virtual desktops to users. After some time, IT administrators need to maintain and update the virtual desktops. The process just requires configuring the update in the template VM, taking a snapshot of it, and then updating virtual desktops based on the snapshot.
The problem is that in every update, there will be another Master Image and the related Differencing Disk created which means that the storage consumption is doubled during the update progress. Although the original Master Image and Differencing Disks will be automatically deleted later, IT administrators should prepare enough storage for update every time.
The load of Master Image I/O reading is easy to understand because all the VMs in the directory will read the same Master Image at the same time. If it is the HDD disk, the performance of virtual desktops will be badly influenced.
To make sure that virtual desktops can always work in good condition, you should backup the virtual machine.
Vinchin Backup & Recovery is the professional XenServer backup solution which is verified by Citrix. You can backup your VM agentlessly with a user-friendly web console. There are multiple useful backup strategies to configure all kinds of backup jobs and Instant Recovery technology will let you recover the failed VM in 15 seconds.
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Citrix is the leading desktop virtualization solution supplier and the MCS mode is the feature to help IT administrators easily do virtual desktop batch provisioning and management jobs by using the Master Image and other disks.
To make sure that virtual desktop can work in good condition, the underlying hypervisor should be backed up so you can try Vinchin Backup & Recovery to backup the XenServer host. Don’t miss the free trial.
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