Steve Pope
Greg Law, Kieran Mansley, Steve Pope, Dickon Reed, David Riddoch.
Solarflare Communications Inc.
The Convergence of Storage and Server Virtualization
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The advent of storage virtualisation in the 90s and server
virtualisation in the 2000s has brought about huge efficiencies in terms
of data center deployments and has been a driving force towards
consolidation on the latest high-performance server platforms. At the
same time, virtualisation is challenged in a number of respects.

- The storage demands of data center applications are increasing
dramatically. For example, many financial institutions report data
doubling every 6 months. Delivering this data demands high bandwidth
networks and I/O server systems.

- Scalable storage and high-performance networks have caused
divergence, with data centers being required to bear the overheads  of
supporting multiple different network types.

- The flexibility of server virtualisation comes at the cost of I/O
performance. This bottleneck has been perceived to be a hindrance  to
greater levels of virtualisation deployment.

This talk will present a perspective on how these challenges have been
met by industry. In particular:

- 10GBASE-T Ethernet promises to support convergence of storage and LAN
traffic onto a single low cost and easy to use network.

- ISVs are responding to the demands of supporting efficient I/O for
virtualised operating systems with features such as virtualised
Ethernet controller interfaces.

- Software vendors have made significant investments into iSCSI
implementations, providing a robust, yet low-cost and  high-performance
storage platform.

In doing so, we describe the extensions to the Xen Front and Back end
driver APIs which have recently been submitted / accepted into the Xen
driver model. This hardware agnostic extension enables ISV provided
guest plugins to provide acceleration features, such as hypervisor
bypass to a suitably aware guest. This may be achieved while supporting
important management features such as guest migration.

We provide data which illustrates the performance of iSCSI traffic over
a 10GBASE-T Ethernet link for three configurations:

- iSCSI stack in Dom0
- iSCSI stack in DomU
- iSCSI stack in DomU + hypervisor bypass

and show that there are significant performance and scalability gains
from the iSCSI stack being present in DomU with bypass enabled.