Multiple desktops getting provisioned at the same time can put significant strain on a number of system resources, especially the storage subsystem because of a heavy load of sustained I/O operations performed by the desktop OS during boot time. An under-provisioned disk subsystem from IOPS capacity perspective can result in broken desktops as desktops fail to start on time or failure to start a number of Windows services on the desktops including HDX service as well as users of previously provisioned desktops experiencing slowness/connectivity issues.

Background

The most significant cause of boot-storm related issues is that the desktops are saturating IOPS capacity of the server, which can result in broken desktops or failure to start critical services on the desktop.

Recommendation

A typical desktop refresh generally consists of 60-70% read operations and 30-40% write operations to the disk subsystem, and approximately 150 IOPS per pooled (aka dynamic) desktop occur during a boot. A personal desktop refresh though generally consists of between 400-450 IOPS during a boot. Your server’s storage system’s IOPS capacity depends on a number of factors including disk rotational speed, disk type (traditional disk or SSD), RAID configuration, RAID controller cache etc. How to calculate your storage subsystem’s IOPS capacity is documented in the VDI-in-a-Box server sizing guide at http://www.citrix.com/content/dam/citrix/en_us/documents/products-solutions/vdi-in-a-box-server-sizing-calculator.xltm

If your VDI-in-a-Box deployment is encountering issues such as broken provisioned desktops, slowness encountered by the existing users when new desktops are provisioned, HDX service not running on a newly provision desktops, Citrix recommends adjusting the number of starting desktops in the Advanced Properties of VDI-in-a-Box Administrator console. There are two settings which control the number of desktops provisioned per server in a VDI-in-a-Box grid:

• Max number of starting desktops (default is 20 per server)

• Max number of starting personal desktops (default is 5 per server)

By decreasing the max number of starting desktops value, the VDI-in-a-Box server will provision fewer desktops at a time, resulting in a reduced IOPS load on servers in the grid. Each customer environment is different and therefore adjust the max number of starting desktops to fit your requirements.

Multiple desktops getting provisioned at the same time can put significant strain on a number of system resources, especially the storage subsystem due to a heavy load of sustained I/O operations performed by the desktop OS during boot time. An under-provisioned disk subsystem from IOPS capacity perspective can result in broken desktops as desktops fail to start on time or failure to start a number of Windows services on the desktops including HDX service as well as users of previously provisioned desktops experiencing slowness/connectivity issues.