Moving to the cloud offers a number of benefits, and there's a reason why it's estimated that over 90% of enterprises have adopted cloud storage platforms. While tools like Movebot can move files from on-prem to the cloud with ease, there's often one stubborn legacy system in your infrastructure stack that's a challenge: the SFTP server. While you've successfully moved databases, applications, and even mainframe workloads to the cloud, that old SFTP server continues to handle critical business file transfers that your organization depends on daily.

SFTP-at-scale

Troubles with SFTP at scale

While it might seem like a "legacy" protocol, it's still one of the most widely used, and sometimes, the only option for older or proprietary systems. But scaling it can be difficult, especially as the business grows, transfer volumes increase, and the number of trading partners expands. Purchasing more servers requires more space, more management, and greater risk. 

Fortunately, there's a better way to deal with SFTP at scale by using a modern file transfer architecture. Scaling SFTP beyond a single server, even to hundreds, can be done without additional hardware, space, or maintenance with the right solution. 

The Complexity of SFTP scalability

SFTP appears deceptively simple on the surface—it's a straightforward protocol for transferring files securely, and one that's been around for decades. But as your organization grows, the complexity compounds exponentially. Moving files is just one portion of managing the server; you also need to monitor user accounts, authorization, compliance, and performance across dozens or hundreds of business-critical workflows.

The traditional approach of running SFTP on a single server with local user accounts breaks down quickly when you need to support multiple availability zones, implement role-based access controls, integrate with identity providers, and maintain audit trails that satisfy GDPR, HIPAA, or other compliance requirements. 

This problem grows considerably when you add more servers to the mix. Hardware, software, and connections need to be managed properly to ensure there isn't a break in critical processes and that any security flaws are quickly patched. 

Architectural Patterns for Scalable SFTP

The Multi-Tier Approach

Modern SFTP architectures separate concerns into distinct layers with different functionality. This separation allows you to scale each component independently and replace individual layers without disrupting the entire system.

For instance, storage nowadays is often separate from the SFTP servers themselves--connecting virtual folders in cloud storage for example--while maintaining the familiar directory structure you and your partners expect. This separation is crucial for achieving true horizontal scalability—you can spin up additional SFTP gateway instances without worrying about data consistency or synchronization, because all instances can connect to the same cloud folders instead of relying on numerous on-prem drives.  

Event-Driven Integration Patterns

Traditional SFTP implementations rely heavily on cron jobs and polling mechanisms to detect new files. Modern architectures often use event-driven patterns, where events like file uploads immediately trigger the next step or even a series of steps in a workflow. 

When files arrive or only need to be transferred at regular intervals, simple scheduling can be configured in many modern platforms too. For instance, files in a folder could be sent daily at a specific time using an automated process that ensures stability without manual procedures. 

Smart scaling

One of the biggest challenges of SFTP at scale is solving how to scale it when needed. With traditional setups, that can involve planning for usage spikes ahead of time, making sure there is available bandwidth and processing power for the increase. 

Modern architecture can simplify or even eliminate this concern. 

SFTP servers that are in the cloud are often able to scale to meet changes in usage patterns on their own. For some, this is by shifting loads to virtual machines that are in reserve just for this purpose. In more elegant architecture, these shifts and scaling are all done automatically as needed, without the user having to have their own licensed VMs in reserve just in case. As loads increase and decrease, the platform will automatically adapt to your capacity needs. 

How exactly this is done will depend on the specific platform, but often involves one or more performance optimization strategies. 

Performance Optimization Strategies

Connection Pooling and Multiplexing

SFTP's connection-heavy nature creates bottlenecks as you scale beyond a few hundred concurrent users. Connection pooling and multiplexing allow multiple operations to share connections, significantly reducing the overhead of SSL handshakes and authentication to improve performance. 

While the speed increases are considerable, there are some potential drawbacks to these approaches. Sessions can be dropped and there can be issues with authentication, causing potential hangups or connection failures, especially when not configured properly. 

Modern architecture will either allow a user to enable these settings or in some cases implement them as needed without manual input. 

Intelligent Load Distribution

Just like with rotating sales reps, simple round-robin load balancing rarely produces optimal results for SFTP workloads. Instead, a better approach is to use intelligent load distribution to choose the best available machine(s) to handle the job, considering factors like file size, transfer duration, and resource requirements. This means loads are shared and distributed, allowing for more efficient results. 

Modern options can go even further, considering factors like current server load, client geolocation, and historical transfer patterns. Simply distributing the existing load in a better manner can greatly improve performance. 

Bandwidth Management

Not all file transfers are equally important. Overnight batch processing can tolerate higher latency and variable throughput compared to real-time trading data that requires guaranteed results with minimal delay. To account for this, modern SFTP platforms provide granular bandwidth controls at the user, group, and directory level.

Rate limiting prevents individual users or processes from consuming all available bandwidth, while traffic shaping can prioritize time-sensitive transfers during business hours. These controls become essential as your SFTP infrastructure scales beyond a few dozen concurrent users. In traditional setups, these controls may need to be set manually, if they're available at all. With modern architecture, however, they can be adjusted on the fly to meet the needs as they appear without guesswork.  

Monitoring and Observability

Beyond Basic Logging

Traditional SFTP monitoring focuses on basic metrics like connection counts and transfer volumes. While important, these are only part of the picture.

A full view gives insights into behavior patterns and performance trends, as well as potential security threats like detecting unusual user behaviors. For instance, user authentication logs can help show if someone is attempting to gain access to the server; and if they've found a valid username. 

Compliance and audit trails

Compliance frameworks require detailed audit trails that capture the who, what, when, and where of events. Modern SFTP audit logs should integrate with other systems and provide sufficient detail to meet required compliance standards and simplify investigations should they be needed. 

Automated compliance checking can help by validating that file transfer activities comply with established policies and flag potential violations for investigation. This is particularly important in regulated industries where file transfer patterns must comply with specific rules or regulatory requirements, and help reduce the likelihood of compliance breaches. 

Proactive Alerting

The goal of monitoring isn't just to collect data, but to turn that data into actionable insights. Modern monitoring systems can detect anomalies in transfer patterns that might indicate compromised accounts, struggling or failing processes, or performance degradation and either recommend or outright fix performance issues before they surface. 

For example, imagine that you're working with a trading partner whose file transfers always arrive on time. If transfers for that normally punctual partner are running 30 minutes late, it could indicate a problem worth investigating before it becomes a business-critical issue, and proactive alerting could notify admins of such concerns to see if they're worth looking into further. 

Migration Strategies 

When the business relies on critical transfers that can't afford to be interrupted, a migration might seem like the worst idea there is. After all, what could be more disruptive than moving entire server workloads, including users, connections, and the transfer workflows themselves? The perceived risk of disrupting established file transfer workflows often outweighs the clear benefits of modernization.

There are a few different migration strategies to help make moving SFTP workloads to the cloud possible. 

Lift and Shift

A Lift and Shift migration is the process of moving an exact copy of an application or workload as is to the cloud, often with a single window of downtime. The problem with this method is that some of the legacy methods may not be compatible in the cloud, which can cause errors and failures.

While this can work in some cases, there are a few different approaches to allow you to modernize SFTP workloads without disruption to normal operations. 

The Parallel Path Approach

Rather than attempting a big-bang migration, one option for modernization is running old and new systems in parallel. This allows you to validate functionality, performance, and reliability without risking disruption to critical business processes. Once you're sure that critical processes are functioning as expected on the new server, you can remove them from the old system. 

The key is making the parallel systems truly independent while maintaining data consistency between them. This often requires careful coordination of user access patterns and transfer operations during the transition period.

Staged Migration by Risk Profile

Not all SFTP users present the same level of risk or complexity. Start migrations with internal users and low-volume partners before tackling your highest-volume, most business-critical integrations. This allows you to identify and resolve issues while minimizing potential business impact.

Create clear criteria for categorizing integrations by risk level, considering factors like transfer volume, business criticality, technical complexity, and partner flexibility. High-risk migrations may require dedicated project resources and extended parallel operation periods.

Moving users and permissions

If there are a large number of users on the existing system, making sure everyone is moved over properly can take some effort. Migrating resources between users carries risk, so it's important to ensure the permission levels are correct before doing this. While this approach is faster, recreating permissions for a new user is less risky, as they can be reviewed and adjusted if needed during user creation. 

Some SFTP solutions simplify the process by autogenerating users or by giving the option to add users in bulk through a method like CSV upload. This may include the option to restrict feature access and isolate users to a specific root directory as well.

Solutions for modernizing SFTP 

Modernizing SFTP infrastructure represents more than a simple technology upgrade—it's an opportunity to fundamentally improve how your organization handles secure file transfer workflows. While the SFTP protocol has remained roughly stable for decades, the approaches to utilizing it have improved with modern advances. And while many organizations have moved other processes like storage to the cloud, SFTP is often for the last mile of the cloud journey. 

That mile doesn't have to be the most difficult. With proper planning and the right solution to move to, modernizing SFTP can provide your organization with numerous benefits while minimizing headaches. 

For many organizations, the right fit is a solution like Couchdrop. Couchdrop is a cloud-native SFTP server and managed file transfer platform that combines FTP, AS2, and SFTP file transfers with automations and multiple document collection methods. With over 20 native integrations with cloud storage platforms as well as remote servers and on-prem systems, b2b file exchange is simple, straightforward, and scalable thanks to the modern cloud architecture that requires no infrastructure management. 

Try Couchdrop free for 14 days to see how modern SFTP can benefit your organization, with no credit card required. Register now to get started.