In finalizing DCIG’s TOP 5 research into general-purpose NAS appliances used as backup targets, I made a notable observation. I found few articles that provide guidance on which default file protocol that organizations should use for backups. That omission may seem trivial.
However, organizations continually seek ways to accelerate backups and recoveries. Something as simple as choosing NFS over SMB, or vice versa, could potentially improve performance. Since all network attached storage (NAS) appliances positioned as backup targets support both protocols, why not select the better one?
The question then becomes whether NFS or SMB should serve as the default file protocol for backups for your organization. If organizations can freely choose, they should start with NFS. Choose SMB primarily when Windows integration, application requirements, or storage-specific capabilities provide a compelling reason.
NFS Makes Sense as the Default File Protocol for Backup
Backup traffic typically consists of sustained data transfers and potentially many concurrent streams. NFS provides a straightforward way to present remote file storage to backup servers. It can also accommodate numerous simultaneous backup streams and connections.
NFS fits particularly well with the Linux-based infrastructure increasingly found in enterprise data protection environments. Organizations can directly mount NFS storage to Linux-based backup servers. This approach avoids introducing Windows-specific authentication or infrastructure solely to access backup storage.
Broad storage system support also strengthens the case for using NFS. DCIG has already formally evaluated over 30 NAS appliances that storage providers position as backup targets. Each of these 30+ models support both NFS and SMB, along with other storage protocols. This widespread support gives organizations considerable flexibility when selecting storage for backup.
Organizations should still distinguish between NFS versions, particularly NFSv3 and NFSv4.1. The term NFS does not describe one implementation with identical capabilities. Organizations should verify which NFS versions their backup application and storage system support.
NFSv3 remains widely supported and offers a simple, mature protocol for carrying backup traffic. However, NFSv4.1 adds sessions, stronger security options, improved locking, and better recovery from connection disruptions. It also consolidates more file operations into a modern stateful protocol.
From an architectural perspective, organizations should give preference to NFSv4.1 as their default file protocol when their backup application and storage system fully support it. Its sessions and improved connection recovery make it better suited for resilient enterprise backup environments. Use NFSv3 when compatibility, application requirements, or proven storage optimizations favor it.
NFS need not outperform SMB in every benchmark to become the default file protocol for backup. It must simply deliver straightforward, broadly supported, high-performance connectivity appropriate for backup workloads. Organizations can then consider SMB when specific requirements justify departing from NFS.
Organizations should also note that all the NAS appliances positioned as backup targets support both NFSv4.1 and SMB 3.x. Support for these protocols may serve to differentiate these NAS appliances from other available in the marketplace. It may also help explain why other NAS appliance providers do not explicitly position their solutions as backup targets.
Modern SMB Remains a Strong File Protocol for Backup Option
While NFS makes a strong case for being the default file protocol for backups, organizations should not immediately dismiss SMB. Legitimate technical and operational reasons exist for choosing SMB instead. This particularly applies to organizations operating predominantly Windows-based backup environments.
SMB’s Windows heritage makes it especially well-suited for Windows-centric infrastructure. Active Directory integration can simplify authentication, permissions, and administration of backup storage. Existing Windows expertise may also make SMB easier to deploy and manage.
Modern SMB 3.x also differs significantly from earlier SMB implementations associated with poor performance. It possesses three attributes that can specifically contribute to improved backup performance. These include:
- SMB Multichannel can establish multiple network connections between backup servers and storage. These connections can increase backup throughput while providing additional network resiliency.
- SMB Direct uses RDMA to transfer data directly between systems with less CPU involvement. This capability can reduce latency and CPU overhead while supporting high throughput.
- SMB Continuous Availability can maintain file access through certain storage-system disruptions.
A properly implemented SMB 3.x environment can therefore provide an excellent transport for backup traffic. Organizations should then give preference to SMB when its capabilities address specific application, integration, performance, or operational requirements. The argument for SMB becoming the default choice may particularly hold true in Windows environments.
Know When to Override the NFS Default File Protocol and Use SMB
Organizations should override the NFS default file protocol when their backup application requires or explicitly recommends SMB. Vendor certification or optimization for SMB provides another compelling reason. These application-specific requirements should take precedence over a general protocol preference.
Windows-centric backup environments may also favor SMB because of its native integration. Active Directory can simplify authentication, permissions, and administration across backup servers and storage. Existing SMB expertise and operational procedures may further reduce management complexity.
Storage capabilities may provide another reason to select SMB. Some storage systems implement SMB capabilities unavailable or less developed through their NFS interfaces. Organizations should compare each storage system’s actual protocol implementation rather than relying solely on protocol specifications.
Performance may also justify overriding the NFS default file protocol. SMB Multichannel can provide additional throughput by utilizing multiple network connections. SMB Direct with RDMA may further improve performance when supported across the entire backup data path.
However, organizations should not select SMB merely because Windows servers exist in their environment. Choose SMB when it provides a demonstrable application, operational, reliability, or performance advantage. Otherwise, organizations may unnecessarily inherit a protocol decision based largely on historical practices.
Protocol Implementation Can Matter More Than Protocol Selection
Choosing NFS does not guarantee better backup performance. Backup throughput depends upon every component in the data path. A bottleneck anywhere along that path can minimize or eliminate performance differences between protocols. These may include:
- Concurrent backup streams. More simultaneous streams can increase aggregate throughput by better utilizing available storage and network resources. Too many streams can instead overwhelm storage controllers, processors, or media.
- TCP connection count. Multiple TCP connections can distribute backup traffic and increase aggregate throughput. Too few connections may prevent backup applications from fully utilizing available network and storage bandwidth.
- Network interface speeds. A saturated network interface creates a performance ceiling regardless of the file protocol used. Faster interfaces may expose protocol differences that slower network connections conceal.
- Number of storage interfaces. Multiple interfaces can distribute incoming backup traffic across additional network paths. A single storage interface may become the bottleneck before either protocol reaches its potential.
- SMB Multichannel. SMB Multichannel can establish multiple connections between backup servers and storage. Properly implemented, it can increase throughput and resiliency enough to overcome an otherwise perceived NFS performance advantage.
- NFS connection parallelism. Multiple NFS connections can distribute backup traffic across available network and storage resources. Greater parallelism may substantially increase aggregate throughput for highly concurrent backup workloads.
- RDMA. RDMA can move data between systems with less processor involvement and fewer memory copies. Its lower CPU overhead and latency can substantially improve performance when supported throughout the data path.
- Network latency. Higher latency increases the time required for protocol requests and acknowledgments to traverse the network. These delays can restrict throughput regardless of available storage performance or network bandwidth.
- Storage architecture. Controller design, caching, file systems, storage media, and scale-out architectures can materially affect backup throughput. These differences can easily outweigh performance differences attributable solely to NFS or SMB.
- Backup application’s protocol implementation. Backup applications may use NFS and SMB differently, including how they establish connections and manage concurrent streams. These implementation differences may favor one protocol regardless of its theoretical capabilities.
These variables explain why organizations should cautiously interpret benchmarks that declare either NFS or SMB faster. An optimized SMB implementation can outperform poorly configured NFS, and vice versa. Start with NFS as the default file protocol but do not assume that NFS will always deliver better performance.
“Fast Enough” Matters More Than Winning the Protocol Benchmark
Organizations need enough performance to satisfy their backup windows and recovery objectives, not necessarily the fastest protocol available. Performance beyond those requirements may provide little operational benefit. Organizations should therefore establish their performance requirements before comparing protocols.
For example, an organization may need 5 GB/s to complete backups within its required window. Properly configured NFS delivers 9 GB/s, while SMB delivers 11 GB/s. SMB wins the benchmark, but both protocols comfortably satisfy the organization’s backup requirements.
Switching to SMB simply to gain unused performance may introduce unnecessary operational complexity. Its additional throughput provides little value unless requirements increase or other SMB capabilities justify switching. In this situation, organizations should continue using NFS.
Conversely, suppose NFS delivers 4 GB/s while SMB delivers 7 GB/s against the same requirement. SMB now provides a measurable advantage that solves a legitimate business problem. This example illustrates that organizations should only change protocols when doing so solves a problem.
Start with NFS; Move to SMB for a Reason
Organizations often establish defaults across their IT environments to simplify operations. Advising them to choose NFS or SMB as their default file protocol based upon “it depends” offers little direction. A default provides a starting point while still permitting exceptions when justified.
DCIG recommends organizations choose NFS as their default file protocol for carrying backup traffic. NFS offers broad storage support, relative simplicity, and natural integration with Linux-based infrastructure. Its characteristics also make it well suited for highly concurrent backup workloads.
Alternatively, organizations should choose SMB when specific requirements justify overriding the NFS default. These include application requirements, Windows integration, SMB Multichannel or RDMA, and demonstrated performance advantages. In short, start with NFS but implement SMB when doing so solves a specific problem.
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