VDI in a Box
Before going into detail about Boot Storms and IOPS, it is important to let readers know what VDI in a Box is if you don’t already know. VDI in a Box, from Citrix originally started life as Kaseya’s VDI in a Box.
This desktop provisioning software cleverly enables users to deploy low maintenance VDI solutions within their organisation. The solution in the background utilises cloned instances of desktops, simplified user management and desktop brokering. For a more detailed look at the solution then take a look at the video below or read our white paper on the fundamentals of VDI.
IOPs – Boot Storms
The downside of concentrating the location of desktops is that this activity also means that we unfortunately concentrate the disk\storage overhead required to support each of those desktops. All desktops require somewhere to store data and reading data from a disk has a performance overhead. Instances where multiple requests for data come in a the time and those request overwhelm the storage physical ability to retrieve that data from the storage, that is known as a boot storm. This typically happens when multiple desktops first boot up hence the term ‘Boot Storm’. Certain boot-storm related issues can arise in VDI in a Box. This happens when the server’s IOPS capacity saturates. The after effects of this issue are also fatal. This results in failure that hinders desktop from opening important services. This break in desktop is not healthy for the overall system.
The bad thing is that when many desktops are provisioned at the same time, the system resources are put under tremendous pressure. During boot time the desktop’s storage subsystems are especially under strain due to performance of operations by the desktop operating system on the desktop. A good bit of info that you should know about is that during a boot about 150 IOPS per pooled desktop takes place. On the other hand desktop refresh constitutes 30 to 40 percent write operations while 60 to 70 percent read operations. However, when PC refreshes it boots at around 400 to 450 IOPS. Different servers have different IOPS capacity. The IOPS capacity of servers is dependant upon many factors, common among them are disk type, RAID configuration and disk rotational speed. One can figure out the IOPS capacity storage subsystems only by knowing the right steps to follow. There are online guides available that can help you to do just that. One kind of guidance available online is that of VDI in a box server sizing guide.
There are some common problems that you can encounter. Sometimes when new desktops are provisioned existing users may encounter slowness of the computer. Secondly problems in VDI in a box deployment can result from broken provisioned desktops. You can also encounter the problem when HDX fails to run on new provision desktops. However, the good news is that these problems can be remedied. The solution to them is that number of desktops should be adjusted. This can be done by going to the VDI in a box Administrator console and then into the advanced settings. There are basically two settings in VDI in a Box grid that control the number of desktops per server. One is the maximum number of starting desktops and the other is the maximum number of staring personal desktops. The default for first setting is 20 per server while the default number of the second type is 5 per server. The servers in the grid are under IOPS load which can be reduced by using lesser number of starting desktops.