By Fred Schimscheimer, Sr. Technical Marketing, End User Computing
Are you tired of stressing out your servers and storage? Do you want to reduce your IOPS?
If the answer is yes, you should take a look at the VMware View Storage Accelerator (also known as Host Caching) for View desktops. Content-Based Read Cache (CBRC) is part of vSphere 5.0 and has been integrated into VMware View 5.1. One performance bottleneck is the I/O requests issued from a virtual machine to the underlying storage for accessing the data contents from its virtual machine image. The View Storage Accelerator addresses this bottleneck by leveraging the CBRC feature in vSphere that provides a per-host RAM-based solution for View desktops. This considerably reduces the read I/O requests that are issued to the storage layer and also addresses boot storms.
Many large VDI deployments will see performance improvements during a boot storm with a large number of cloned virtual machines, especially when the boot storm is highly read-intensive and multiple virtual machines issue read requests for data blocks that have identical content. Additionally, the View Storage Accelerator is beneficial when disks contain the same content irrespective of where it comes from.
Greg Pellegrino at Pivot3 did some early testing of the View Storage Accelerator and here is what he found. The chart below shows the read rate of the SSD tier. The desktops are Windows 7 with recommended settings for View applied.
Figure 1: Graph courtesy of Pivot3
The timeline shows:
- Time 12 – 67: Login storm
- Time 170-232: Media player file reads from RAWC pass 1
- Time 340-405: Media player file reads from RAWC pass 2
5.0 and 5.1 refer to View version.
Reboot refers to a test run immediately following the desktop boots. No Reboot is a subsequent test run without rebooting desktops.
CBRC Impact:
- At the login storm when logins immediately follow the desktop reboots. This corresponds with Windows loading of executables to transition into a user runtime state.
- Reads of the large media files from disk. The first desktop that reads these files causes them to get cached into CBRC. Then the other desktops get cache hits.
To take advantage of this functionality in vSphere you’ll need VMware View 5.1 and latest service pack. Configuring the View Storage Accelerator is done through the View Administrator console and is just a one step process when configuring a pool. The View Storage Accelerator is supported for any vCenter-Managed View Desktops such as manual desktops, automated full clone desktops and automated linked clone desktops.
To learn more about the View Storage Accelerator, visit this white paper: View Storage Accelerator in VMware View 5.1
