Convergence

The diagram shows technologies that are part of the drive toward converge of storage, server and network technologies in the data center.

Virtualization and the need to support virtual machine mobility (e.g. vMotion/XenMotion/Xen Live Migration) is driving the adoption of large, flat, high-speed, layer-2, switched Ethernet fabrics in the data center. A layer-2 fabric allows a virtual machine to keeps its IP address and maintain network connections when it moves (performing a "live" migration).

Networked storage (iSCSI, NFS, FCoE) is also needed to support virtual machine mobility. In addition, moving storage from dedicated SANs to a converged Ethernet fabric reduced cabling and networking costs and improves flexibility. However, migration of storage traffic onto a converged Ethernet fabric dramatically increases bandwidth demands and is one of the factors accelerating the adoption of 10/40/100G Ethernet.

Ethernet standards are evolving to address the needs of convergence. As well as higher speeds, IEEE data center bridging standards add support for lossless Ethernet to improve storage performance and support Fiber Channel over Ethernet (FCoE). The performance and stability of large layer 2 Ethernets is being addressed through new protocols such as shortest path bridging.

Changes are not limited to storage and data networking. Server architectures are changing as convergence blurs the line between the server and the network, extending the Ethernet fabric into servers through blade switches, network adapters and virtual switches.

The current siloed approach to managing storage, servers and networks no longer works in a converged environment where each of these areas is so closely inter-dependent. Fortunately, convergence to an Ethernet fabric brings with it the data center visibility needed to manage the converged data center.

The sFlow standard, implemented by most vendor's Ethernet switches, simplifies management by providing the unified visibility and control needed to fully realize the benefits of virtualization and convergence.

Networked storage

A previous posting discussed how sFlow is used to provide visibility in the data center. This post looks more closely at the challenge posed by networked storage.

There are many good reasons to use networked storage: the storage resources can be shared, replicated and backed up independently of the systems that use them. In a virtual server environment, using networked storage for the virtual machine images simplifies the replication of virtual machines and the migration of virtual machines between servers (e.g. VMWare vMotion, Citrix XenMotion or Xen Live Migration).

In addition, the migrating of storage from a dedicated storage area network (SAN) to a single Converged Enhanced Ethernet (CEE) network promises to reduce cost and create a more flexible data center infrastructure. However, this migration also places additional demands on the LAN infrastructure.

Regardless of the type of networked storage (iSCSI, NFS, AoE or FCoE), the management of network bandwidth is critical to successful deployment and operation. For example, the chart above shows site-wide traffic from a large campus network broken out by protocol. The storage traffic (iSCSI) is clearly the largest load on the network, dwarfing the amount of web (HTTP) traffic.

The visibility into network traffic provided by sFlow is critical to effectively managing network resources. If the network is poorly provisioned, congestion associated with storage traffic will degrade quality of service (QoS) for other applications on the network and impair system performance since network congestion will also manifest itself as slow disk performance.