Storage network choices for virtualization: A guide

Choosing a storage network is like selecting sunglasses. Cost, style and support are all vital considerations. For storage networking, there’s Fibre Channel, iSCSI or FCoE.

Servers often take center stage when it comes to virtualization, but no deployment is complete without careful

consideration of the storage network. Virtual machines (VMs) are little more than files that operate in server memory. A VM still loads from and saves to storage, so IT pros must adopt the most appropriate storage networking infrastructure for their virtual data centers.

Shared storage is often a minimum requirement, and experts agree it’s critical to consider for virtualization storage networks. Locking a VM within a server’s local disk would essentially prohibit critical features such as live migration or backup services. But when it comes to planning for shared storage, virtualization storage costs affect the choice of storage array, the network and switching infrastructure carrying storage data, and the interfaces deployed at each server.

Beyond shared storage, the real choice with storage networking is between network-attached storage (NAS) and other storage area network (SAN) architectures such as Fibre Channel, Internet SCSI (iSCSI) and Fibre Channel over Ethernet (FCoE). Before jumping on the latest technology, it’s important to understand the critical attributes of storage networking in a virtual environment and to weigh the pros and cons of each storage network.

This series will help you understand the storage networking options so you can decide which method best fits your infrastructure.

Part one: Shared storage considerations: Management, throughput, costs
Shared storage is ideal for virtualization because it allows VMs to use storage outside a single local disk. Management is an important factor with shared storage, because admins need to track numerous logical unit numbers and be able to easily see resource usage. Throughput is another consideration; with multiple VMs on a single physical host, there is often storage network contention.

Part two: Why choose Fibre Channel for virtualization storage networking?
Fibre Channel is known for its performance and security in virtualization storage networking. It provides a high-bandwidth, low-latency storage network that’s well suited for handling aggregated storage traffic. It’s fairly simple to expand an existing Fibre Channel SAN, but if you’re building from scratch, cost and management are major concerns.

Part three: Pros and cons of iSCSI storage networking in virtual infrastructures
ISCSI provides simplicity for virtualization storage networking, but performance, network design, security and cost can present challenges. Ethernet problems such as bottlenecks and latency can also create issues with traffic and subsystems. ISCSI storage networking traffic is passed along the LAN, so it’s also easier for traffic to be compromised by malware and passed to the Internet. Still, you can improve iSCSI performance by using specialized iSCSI host bus adapters that alleviate some of the processing overhead.

Part four: FCoE considerations with virtualization: Support, SAN integration
Fibre Channel over Ethernet improves storage network reliability, and admins generally find it’s easy to integrate FCoE with Fibre Channel SANs and management software. But not all vendors support FCoE for storage networking. FCoE does not easily stack on Ethernet like iSCSI does, and your server network adapters and switches must be FCoE-compliant models.

This was first published in June 2011

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