Every IT professional’s goal is to improve TCO. In a Virtual Desktop Infrastructure (VDI) application, the objective is to increase the efficiency by maximizing the number of virtual desktops per server while maintaining response times to users that would be comparable to a physical desktop. In addition, the solution must be resilient since downtime of the VDI application causes the idling of hundreds to thousands of users and consequently reduces overall organizational productivity and increases user frustration.
Low latency data requests from storage or other servers are the key to enabling more VDI sessions without increasing user response times. Legacy Fibre Channel-connected storage subsystems provide shared storage which enables moving virtual machines between physical servers. Leveraging an existing Ethernet infrastructure saves costs by combining networking and storage I/O over the same cable. iSCSI Extensions for RDMA (iSER) is a computer network protocol that extends the Internet Small Computer System Interface (iSCSI) protocol to use Remote Direct Memory Access (RDMA). It basically uses the upper layers of iSCSI for session management, discovery, recovery, etc., and thus compatible with all the features and functions supported by iSCSI. However, using iSER eliminates the bottleneck through the following mechanisms:
- Uses zero copy via RDMA technology
- CRC is calculated by hardware
- Works with message boundaries instead of streams
- The transport protocol is implemented in hardware (minimal CPU cycles per IO)
Recently, at VMworld’13, LSI Corporation and Mellanox Technologies presented a joint solution that accelerates the access storage. The solution includes LSI’s Nytro MegaRAID NMR 8110-4i card which has 200GB of on-card flash and eight SAS HDDs and Mellanox’s ConnectX®-3 Pro adapter supports 10Gb/s RoCE storage connectivity between the servers. VDI performance (over TCP/IP and RoCE) was measured using Login VSI’s VDI load generator which creates the actual workload of a typical Windows user using Microsoft Office.
Running Login VSI showed that when running over 10GE TCP/IP only 65 virtual desktop responded within 5 seconds or less, versus 140 when running over 10GE RoCE. This translates into more than 2X cost saving of the VDI hardware infrastructure and proven to be an excellent economical alternative to legacy Fibre Channel based storage subsystems.