TAP (Traffic Access Point)
1: A passive hardware device that provides ‘access’ to optical traffic at a specific point in a network.
1: The act of installing a TAP. Typically used in conjunction with other phrases like “best practice” that refers to the standardized deployment of TAPs. As in: “We TAP as a best practice to ensure access to the optical traffic in our environment.”
Deploying TAPs in the optical networks of the modern data center is a topic of heated debate. TAPs have been common in the TCP/IP world for more than a decade, where they are deployed to provide network access to packet brokers, intrusion detection and security solutions, and performance management solutions. However, the use of TAPs in optical storage infrastructures is much less common and still retains a stigma despite being deployed in some of the largest companies around the world.
Although their use is recognized as a best practice by industry leaders and analysts alike, the full understanding of the benefits that TAPs enable has not yet reached the same level of maturity it has in the broader networking world. Storage administrators often respond with pure, unbridled joy when they see the data that a TAP-enabled monitoring solution can deliver. Physical infrastructure teams, on the other hand, may respond to the idea of TAPs with ambivalence or even apprehension. The level of mixed feelings surrounding TAPs in the storage space baffles me, especially given how well accepted it is in the general networking space.
What is a TAP?
A TAP is a simple device that mirrors the optical signal traveling across a fiber cable. They are completely passive and do not cause latency or degrade the quality of the optical signal. TAPs are enablers. With TAPs in place, IT can deploy out-of-band monitoring and diagnostic devices and have complete visibility into the actual, line-rate traffic on the SAN.
Customers often ask why this is important and the answer is simple. The light doesn’t lie. TAP-enabled monitoring solutions have direct access to the protocol level and the data. There is no device management tool acting as a middle-man trying to interpret what is happening on the physical layer. Until the combination of TAPs and TAP-enabled monitoring solutions emerged as a best-practice, SANs for most organization were impenetrable black boxes—and often blamed for most, if not all performance problems.
TAP into the light
To TAP or Not to TAP is really no question at all because the benefits far outweigh the perceived challenges. Tapping the storage infrastructure when it’s deployed is similar to installing a fire hydrant when your house is built, not when you have a fire. With TAPs in place IT can successfully do everything from firefighting issues to optimizing performance. When a SAN has an emergency, administrators can plug in diagnostic tools without disrupting data flow and quickly discover the root cause. When persistent, ongoing monitoring becomes a requirement, administrators can easily deploy monitoring solutions to gain immediate insight into the actual problems before they result in a noticeable impact to the system. When migrating or consolidating data center components the TAP, together with a monitoring solution, enables IT to establish highly accurate baselines for application performance before the change, monitor throughout the move and then optimize the new systems for maximum performance, availability and utilization going forward.
A simple TAP
The most often heard argument against tapping the storage infrastructure is the installation process. Installing TAPs when new SAN infrastructure is deployed or prior to production is the best practice. That guarantees that the infrastructure will not be disturbed when troubleshooting or optimization is required.
While that’s the ideal scenario, we all recognize that’s not always reality. In some instances, IT needs to tap existing storage infrastructures. In that case, effective change management processes and policies are essential. TAPs can be installed at times of low activity and traffic can proactively be moved to another route so there is no application slowdown or outage during installation. With proper planning, the actual act of tapping the infrastructure takes less than five minutes.
The combination of TAPs and TAP-enabled monitoring solutions are increasingly seen as the optimal method for assuring the performance of mission-critical IT environments. The benefits are clear: faster root cause identification and remediation, the ability to de-risk consolidations and migrations and, ultimately, the ability to optimize performance.