Real Time SAN Analytics, No TAPs – Virtual Instruments & Cisco Briefing Note

Capturing real time analytics from the storage area network is important to optimizing the network. However, the rapid adoption of flash technology makes it even more critical. The problem is capturing information in real time typically involves using TAPs. A TAP enables information to be captured without impacting network performance. The problem is IT professionals are at times hesitant to embed a TAP into their network so they risk their business and tolerate the less accurate sampling approach to collecting data. Cisco recently introduced telemetry streaming into its MDS storage switches, which vendors like Virtual Instruments can take advantage of to eliminate the need for network TAPs but still capture real time information.

The Pros and Cons of TAPs

A TAP is a passive device installed in the network that captures real time data from it and feeds that information back to an analytics engine. The value is that problems can be detected before they are noticed outside of the data center.

The problem is they are akin to a routine, but invasive surgery and the thought of a TAP gives IT professionals unfamiliar with their value pause. TAP installation is not difficult and it is non disruptive, but it does require planning and it does involve taking one side of the SAN down and then the other.

Without a TAP, information about SAN performance and configuration needs to be captured in periodic samples so performance is not impacted – typically 1 to 5 minutes. The longer the time between samples, the less impact there will be on performance, but also the more details that will be missed. It is similar to reading every other page of a book.

Introducing SAN Telemetry

An alternative is for the network switch to provide extra processing power so that real time data can be captured without impacting performance. This is what Cisco has done with its SAN Telemetry offload ASIC. Once delivering the capability, Cisco had a choice to make. Should it keep the capability closed and develop its own performance analytics tools or should it open it up so third parties with deep experience can participate? Cisco choose the path of partnering, which gives it access to the deep expertise from companies like Virtual Instruments, who was exclusively promoted in the Cisco announcement.

A New Deployment Model

Prior to the SAN Telemetry Streaming integration, Virtual Instruments’ VirtualWisdom required the installation of an optical TAP between the MDS switch and the storage array. The TAP passively provided access to the data stream and routed that stream to a Performance Probe. The Performance Probe handled the protocol analysis and generated a statistical summary of what it observed, including workload and response time data for every IO. Finally the Performance Probe pushed the statistical summary to the VirtualWisdom Management Appliance which stores the data and runs analytics on that data.

With the Cisco MDS SAN Telemetry Streaming integration there is no longer a need for the physical TAP or the performance probe. Both are replaced by the dedicated ASIC inside the Cisco MDS switch. The ASIC provides the statistical summary of observed workload response times. The MDS switch then actively streams the resulting summary via its telemetry interface to the VirtualWisdom Appliance.

The result of leveraging the Cisco ASIC and the Telemetry Streaming integration is VirtualWisdom becomes a significantly easier product to implement. It also significantly lowers the cost of real time monitoring as VirtualWisdom TAPs and hardware Probes are no longer mandatory except in the most mission-critical Tier 1 apps. Most customers wait until something goes wrong before seeking out a solution like VirtualWisdom. Now, given the more frictionless implementation IT professionals can get started on the right foot, capturing storage IO traffic in real time and eliminating problems before they cause application problems.

StorageSwiss Take

Proactive, real time management of the SAN has always been a best practice. The problem was getting there, because of the TAP requirement, only occurred after something went wrong. Now VirtualWisdom, at least for Cisco customers, is a simple implementation and allows them to see the value of real time SAN monitoring without having to implement TAPs.

Eight years ago George Crump, founded Storage Switzerland with one simple goal. To educate IT professionals about all aspects of data center storage. He is the primary contributor to Storage Switzerland and is and a heavily sought after public speaker. With 25 years of experience designing storage solutions for data centers across the US, he has seen the birth of such technologies as RAID, NAS and SAN, Virtualization, Cloud and Enterprise Flash. Prior to founding Storage Switzerland he was CTO at one the nation's largest storage integrators where he was in charge of technology testing, integration and product selection.

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