Configuring storage for virtual desktops

The centralization issue

Boot storms create flood of I/Os

Virtual desktop infrastructure (VDI) creates a profile of highly random I/O with the highest IOPS peaks occurring during ?boot storms? when many users attempt to boot up their virtual systems simultaneously. While high-performance storage systems and media such as solid-state drives can help alleviate this problem, the challenge then becomes an exercise within total cost of ownership (TCO) boundaries that justify desktop centralization in the first place.

When desktops are dispersed across the IT infrastructure, the disk capacity they require is generally provided by low-cost SATA drives installed within each physical machine. A directly attached SATA drive is capable of meeting even the maximum I/O demands of a typical desktop. Any performance impact or data loss from a drive will only affect that PC or laptop. As storage is centralized, the potential impact of storage-related problems is significantly increased, with any data loss possibly affecting hundreds or thousands of users. In addition, centralization of desktop data in a VDI environment creates a large random I/O workload profile, which is the most challenging to deliver on storage arrays.

Maintaining adequate I/O performance also requires dealing with large I/O peaks known as ?boot storms.? VDI is user driven and users typically log into their desktops in the morning and log out as they prepare to leave work at the end of the day. Most users logon activity is likely to occur between 8 a.m. and 10 a.m., creating a boot storm that generates a large number of read requests as the desktops start up. Similarly, at the end of the day when users log off, saving their work and closing down their desktops, large amounts of random write I/Os are generated. Both of these peaks must be addressed by the VDI infrastructure as any delay in response translates directly into lost productivity.

This was first published in June 2012

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