Load balancing for highly available medical imaging applications

Load balancing PACS servers ensure high availability and scalability for mission-critical application services. Scalability means the resource is capable of adapting dynamically and easily to increased workload without impacting the existing performance. Server load-balancing divides the amount of work, balancing the load among two or more participating servers and making the server cluster perform as one to end-users. A load-balanced PACS server cluster routes the service requests to the server with the least activity, spreading application service requests to all participating servers, thereby improving the performance of the system.

Load balancers also help with high availability – the ability to continually provide application services and remain accessible and available to end-users even during one or more server failures. When multiple servers are used for combined load balancing and fail-over services, a dedicated load balancer ensures all servers assigned to the task function, and the workload is spread out to all those servers. This helps in implementing failover. Server failover improves fault-tolerance for mission-critical PACS so that when tasks are automatically offloaded from the primary server to a secondary standby server, the procedure is seamless to users at the PACS workstation end.

During normal operations, a load balancer carefully monitors each server of the server cluster continuously. For any reason, if a particular server becomes unresponsive, the load balancer is notified, which then shifts all application service requests to the remaining server(s). No more application service requests are sent to the non-responsive server. So a load balancer facilitates failover and helps PACS continual functionality, achieving some degree of fault tolerance. To sum up, load balancers reduce the risks of downtime, data loss, and data migration delays in PACS, thereby speeding up overall system performance.

As healthcare systems face challenges with data residing in numerous siloed PACS systems at multiple sites, Enterprise Imaging (EI) has emerged as a new enterprise-level solution. Enterprise imaging integrates various imaging systems such as Picture Archiving and Communication Systems (PACS), Radiology Information Systems (RIS), and other specialty-specific imaging systems into a unified platform, transforming it and making it accessible to all – thus helping healthcare organizations unlock, analyze and share information and ultimately become less department-centric and more patient-centric.

While the benefits of enterprise imaging are numerous, it also introduces an additional level of complexity while the dangers of downtime are potentially multiplied. Load balancing has proven to play a key role in mitigating these dangers by ensuring high availability, fault-tolerance and scalability for these mission-critical application services.

More specifically, ADCs (load balancers) ensure EI systems can continually provide application services and remain accessible and available to end-users even during one or more application server failures.

Implementing a load balancing solution can help solve communication issues between cumbersome interfaces, data scalability problems and issues related to accessing and connecting data that resides in numerous, often disconnected health data systems located within one setup or spanning across multiple geographical locations. Load balancing can ensure zero downtime by preventing healthcare systems from falling apart whenever there is heavy traffic or data overload, helping clinicians with continuous data access. And additionally reducing workflow interruptions and employee inconveniences caused due to system failures.

There’s an urgent need to digitize pathology services globally, but it isn’t always straightforward. Huge issues need to be addressed in terms of IT performance, system integration, scalability and data storage, before digital pathology solutions can be successfully deployed. Load balancing can help address these problems and optimize digital pathology solutions in a number of key ways.

ADCs (load balancers) can play a key role in multi-site digital pathology deployment models, enabling data to be shared and replicated across several hospitals. They help to preserve the integrity of the data replicated across sites and prevent data loss. If an outage were to occur in a digital pathology system at one site, it is the load balancer that would step in and redirect user traffic to an alternative location, preventing any interruption in pathology services and delays in diagnosis that could put lives at risk.

There are a variety of load balancing methods, with most addressing the two common modes of operation – Layer 4 and Layer 7. These modes support industry standards like TCP, DICOM, HL7, HTTPS, XDS (Cross Enterprise Document Sharing), SOAP (Simple Object Access Protocol) and XML (Extensible Markup Language).

• Layer 4 offers the strongest performance, forwarding data without inspecting it and simplifying the transaction.
• But with Layer 7, you get greater flexibility.

For most facilities Layer 4 Direct Routing mode is a safe choice, offering peak performance and simple implementation – but this won’t be the case for everyone. The best load balancing solution depends on a lot of factors, from your specific requirements and infrastructure to the type of environment.

Introduction

Load balancers can play a pivotal role in migration projects by helping organizations to mitigate the three significant risks of slow data migration, patient data loss and downtime.

Available as a virtualized solution or as a hardware appliance, load balancers can be placed between the legacy system, existing image capture equipment and new platform, facilitating integration and streamlining the flow of traffic. They can significantly simplify the migration process, whether the project is being led by the organization’s own in-house IT team, a PACS vendor or a specialist medical imaging services consultancy.

High availability during the data migration process

DICOM is the protocol for integrating medical imaging and associated devices to a PACS or EI system. DICOM is also essential for populating a new PACS, VNA or EI system with data.

When a direct-to-media migration is used, DICOM data can be delivered much faster than when a traditional DICOM-based extraction approach is used. Data is therefore delivered in much greater volumes to the new system.

Sitting between the migration engine and the new platform, load balancers stream DICOM data to multiple nodes simultaneously, rather than one, which reduces the likelihood of ingestion bottlenecks and allows the data migration process to proceed efficiently and reliably. When a load balancer is not used, if a receiving node becomes overloaded or goes offline, the entire data migration grinds to a halt.

With a load balancer, if one node becomes overloaded, data migration will automatically switch to other available nodes and the process will continue.

Smooth PACS transition

During a system replacement project, an organization may have a legacy and a new system running simultaneously. Both systems will be delivering services for users while at the same time handling the additional load of the data migration activity, and all scanners and X-ray equipment will still be acquiring new data for patients.

Using a load balancer to reduce bottlenecks should optimize response times on the new PACS and help to deliver a better experience for users while the data migration takes place. It can also allow scanners and X-ray equipment to seamlessly transition from sending new exams from the outgoing system to the new system.

Changing destination IP addresses on scanners and X-ray machines often requires a chargeable engineer visit. However, if a load balancer is used to be the virtual destination IP, and the load balancer’s address can be changed on the X-ray or scanner equipment during a periodic maintenance visit, the need for a separate call-out fee to change the IP address can be avoided. The implementation and timing of changing scanner-to-PACS routing during migration starts to come under the control of the healthcare organization rather than the equipment vendor.

High availability and flexibility after the migration

Load balancers can help to ensure the high availability of the new PACS or EI platform throughout its entire lifetime. Newly balance newly acquired exams across servers in the platform. This ensures that no single server is overloaded and deliver high performance for every user. Some load balancers can undertake multi-layer health checks, verifying not only that the system is available, but also that the storage systems and database are available. It this way, they can help ensure the availability of the entire service for clinicians.

The use of load balancers also makes it far easier for organizations to scale up their PACS platform. The load balancers can easily direct traffic to additional servers, as usage increases and file storage is consumed, preventing degradation in performance over time.