Welcome!

SDN Journal Authors: Daniel Gordon, John Walsh, Elizabeth White, Liz McMillan, Sven Olav Lund

Related Topics: @CloudExpo, Containers Expo Blog, SDN Journal

@CloudExpo: Article

The Rise and Fall of SANTap | @CloudExpo #Cloud

A decade later, the Holy Grail of seamless live data tapping from SAN remains elusive

I am not sure how many people remember Cisco SANTap. About ten years ago, Cisco introduced a data tapping mechanism in the MDS 9000 fibre channel switches. The idea was to allow the data path to be "tapped" at-will. Tapping in this case meant using a mechanism in the switch to split the data being written from client hosts to the storage, allowing the identical "split" data to be routed through a second, separate path.

SANTap therefore allowed a copy of the data to be seamlessly "mirrored" through the switch and subsequently used by other applications for multiple purposes (especially for backup). It facilitated real-time protection of critical data, and allowed advanced functions such as migration, snapshots, etc.

It was a great idea. However while it might sound like a simple solution, the details were exceedingly complicated. Two considerations immediately reveal how convoluted such a seemingly simple proposition could become:

  1. Fibre channel SAN inevitably involves multipath. For a LUN to be protected, all paths involved must be tapped. None can be left out. When using high-availability, this means paths will also travel through another switch. Every bit of data from these paths through different switches must be tapped without missing a single command.
  2. The application or appliance that receives the data must be fast enough to receive real-time tapping. The smallest hiccup in data cannot be tolerated, since the tapping mechanism will not wait for the receiving application or appliance to "catch up," or client performance will be affected. When this happens, SANTap switches to error mode and tracks the changed data in a dirty data map. The appliance then has to perform recovery - meaning copy the missed data first - and get back in sync. Unfortunately, SANTap's primary design intent was for use with backup storage, and organizations rarely implement their highest-performing servers and devices in the backup space. It wasn't surprising then to see these applications and devices struggle with data ingress off the "tap" when administrators tried out this new technology.

These two real-world scenarios are just the tip of the iceberg when it comes to tapping data from SAN. The scope and complexity cannot be exaggerated, and it could be the reason why SANTap was not adopted pervasively by many vendors for their applications. The most recent material referencing the technology was from 2007, where EMC announced SANTap with RecoveryPoint.

Years ago when SANTap was at its infancy, while I was still in my previous company, I met with the Cisco engineering team working on SANTap and tried to persuade them to adjust certain aspects of the feature so we could integrate it into our own data protection product, which was perfect for SANTap. In fact we had already demonstrated a functional version, but were running into issues when many paths were tapped.

However that was another era at another time. For various inexplicable and non-technical reasons, the project just faded into oblivion. There were no other well-known products publicized that used SANTap. Nearly a decade later, the Holy Grail of seamless live data tapping from SAN remained elusive.

That is, until now. Newly available technologies allow third parties to build SANTap-like mechanisms.

Appliances which can tap live data with a Transparent Data Intercept technique have been developed that allow live insertion of interception points into the data path of fibre channel links. This technique is normally described as physical insertion by unplugging the storage or host ports, plugging that connection into the tapping appliances, and then connecting the appliance ports back to the switches. By doing this one link at a time, the data path can be intercepted transparently without downtime, and without any changes to the SAN environment.

This works extremely well. However, the same appliance can be inserted into the data paths without having to physically unplug cables. Using switches that support virtual SAN, such as most Cisco (vSAN) or Brocade (Virtual Fabric) switches, appliances with the Transparent Data Intercept capability can be simply plug into the switch ports, and tap into the data links. No changes to the original cable configuration are necessary.

This technique brought back the memory of SANTap. With an appliance and virtual SAN, this is exactly what it is - simply plug the appliances into the switches, then use virtual SAN to map into the links to be intercepted. Once inserted, the SAN environment is automatically discovered and organized by LUNs and hosts, and all detailed paths can be clearly identified, even across switches. All the related complexity can be hidden by clever software.

The implication is quite significant, if not earth-shattering. This means using this type of technology, after plugging the appliances into the switches and creating a few small virtual SANs, selected storage or host ports can be intercepted seamlessly. The entire SAN configuration can potentially be graphically illustrated. Individual LUNs can be selected and tapped, and the data can be migrated, or backed up for disaster recovery, periodically or continuously, local or remote. In addition, this process can enable cache, anti-virus, or even just SAN system health and performance analysis.

Through advanced Transparent Datapath Intercept technology, this tapping mechanism may soon be opened up via APIs for all storage solution developers to build their own applications - fulfilling the promise originally proposed by SANTap. One can only imagine what other great innovative products people can come up with once this interface is made available.

Come to think of it, maybe Cisco should adopt this and consider it as a "SANTap, redux"...

More Stories By Wai Lam

Wai Lam is co-founder and CTO of Cirrus Data Solutions (www.cdsi.us.com), a developer of Data Migration Server and Data Caching Server for storage area networks (SANs). He was previously CTO and VP of Engineering at FalconStor, a company he co-founded in 2000. There, he was the chief architect, holding 18 of 21 company patents. His inventions and innovations include many industry "firsts" in advanced storage virtualization, data protection, and disaster recovery. Wai received the prestigious China national "Top 1000 Technological Leaders" award in 2013

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


@CloudExpo Stories
"ZeroStack is a startup in Silicon Valley. We're solving a very interesting problem around bringing public cloud convenience with private cloud control for enterprises and mid-size companies," explained Kamesh Pemmaraju, VP of Product Management at ZeroStack, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
In his session at 21st Cloud Expo, Carl J. Levine, Senior Technical Evangelist for NS1, will objectively discuss how DNS is used to solve Digital Transformation challenges in large SaaS applications, CDNs, AdTech platforms, and other demanding use cases. Carl J. Levine is the Senior Technical Evangelist for NS1. A veteran of the Internet Infrastructure space, he has over a decade of experience with startups, networking protocols and Internet infrastructure, combined with the unique ability to it...
"Codigm is based on the cloud and we are here to explore marketing opportunities in America. Our mission is to make an ecosystem of the SW environment that anyone can understand, learn, teach, and develop the SW on the cloud," explained Sung Tae Ryu, CEO of Codigm, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
High-velocity engineering teams are applying not only continuous delivery processes, but also lessons in experimentation from established leaders like Amazon, Netflix, and Facebook. These companies have made experimentation a foundation for their release processes, allowing them to try out major feature releases and redesigns within smaller groups before making them broadly available. In his session at 21st Cloud Expo, Brian Lucas, Senior Staff Engineer at Optimizely, discussed how by using ne...
"There's plenty of bandwidth out there but it's never in the right place. So what Cedexis does is uses data to work out the best pathways to get data from the origin to the person who wants to get it," explained Simon Jones, Evangelist and Head of Marketing at Cedexis, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
"Cloud Academy is an enterprise training platform for the cloud, specifically public clouds. We offer guided learning experiences on AWS, Azure, Google Cloud and all the surrounding methodologies and technologies that you need to know and your teams need to know in order to leverage the full benefits of the cloud," explained Alex Brower, VP of Marketing at Cloud Academy, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clar...
Large industrial manufacturing organizations are adopting the agile principles of cloud software companies. The industrial manufacturing development process has not scaled over time. Now that design CAD teams are geographically distributed, centralizing their work is key. With large multi-gigabyte projects, outdated tools have stifled industrial team agility, time-to-market milestones, and impacted P&L stakeholders.
Gemini is Yahoo’s native and search advertising platform. To ensure the quality of a complex distributed system that spans multiple products and components and across various desktop websites and mobile app and web experiences – both Yahoo owned and operated and third-party syndication (supply), with complex interaction with more than a billion users and numerous advertisers globally (demand) – it becomes imperative to automate a set of end-to-end tests 24x7 to detect bugs and regression. In th...
Enterprises are moving to the cloud faster than most of us in security expected. CIOs are going from 0 to 100 in cloud adoption and leaving security teams in the dust. Once cloud is part of an enterprise stack, it’s unclear who has responsibility for the protection of applications, services, and data. When cloud breaches occur, whether active compromise or a publicly accessible database, the blame must fall on both service providers and users. In his session at 21st Cloud Expo, Ben Johnson, C...
"Infoblox does DNS, DHCP and IP address management for not only enterprise networks but cloud networks as well. Customers are looking for a single platform that can extend not only in their private enterprise environment but private cloud, public cloud, tracking all the IP space and everything that is going on in that environment," explained Steve Salo, Principal Systems Engineer at Infoblox, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Conventio...
Data scientists must access high-performance computing resources across a wide-area network. To achieve cloud-based HPC visualization, researchers must transfer datasets and visualization results efficiently. HPC clusters now compute GPU-accelerated visualization in the cloud cluster. To efficiently display results remotely, a high-performance, low-latency protocol transfers the display from the cluster to a remote desktop. Further, tools to easily mount remote datasets and efficiently transfer...
"MobiDev is a software development company and we do complex, custom software development for everybody from entrepreneurs to large enterprises," explained Alan Winters, U.S. Head of Business Development at MobiDev, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
Agile has finally jumped the technology shark, expanding outside the software world. Enterprises are now increasingly adopting Agile practices across their organizations in order to successfully navigate the disruptive waters that threaten to drown them. In our quest for establishing change as a core competency in our organizations, this business-centric notion of Agile is an essential component of Agile Digital Transformation. In the years since the publication of the Agile Manifesto, the conn...
"We're developing a software that is based on the cloud environment and we are providing those services to corporations and the general public," explained Seungmin Kim, CEO/CTO of SM Systems Inc., in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
SYS-CON Events announced today that CrowdReviews.com has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5–7, 2018, at the Javits Center in New York City, NY. CrowdReviews.com is a transparent online platform for determining which products and services are the best based on the opinion of the crowd. The crowd consists of Internet users that have experienced products and services first-hand and have an interest in letting other potential buye...
The question before companies today is not whether to become intelligent, it’s a question of how and how fast. The key is to adopt and deploy an intelligent application strategy while simultaneously preparing to scale that intelligence. In her session at 21st Cloud Expo, Sangeeta Chakraborty, Chief Customer Officer at Ayasdi, provided a tactical framework to become a truly intelligent enterprise, including how to identify the right applications for AI, how to build a Center of Excellence to oper...
"IBM is really all in on blockchain. We take a look at sort of the history of blockchain ledger technologies. It started out with bitcoin, Ethereum, and IBM evaluated these particular blockchain technologies and found they were anonymous and permissionless and that many companies were looking for permissioned blockchain," stated René Bostic, Technical VP of the IBM Cloud Unit in North America, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Conventi...
SYS-CON Events announced today that Telecom Reseller has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. Telecom Reseller reports on Unified Communications, UCaaS, BPaaS for enterprise and SMBs. They report extensively on both customer premises based solutions such as IP-PBX as well as cloud based and hosted platforms.
While some developers care passionately about how data centers and clouds are architected, for most, it is only the end result that matters. To the majority of companies, technology exists to solve a business problem, and only delivers value when it is solving that problem. 2017 brings the mainstream adoption of containers for production workloads. In his session at 21st Cloud Expo, Ben McCormack, VP of Operations at Evernote, discussed how data centers of the future will be managed, how the p...
In his session at 21st Cloud Expo, James Henry, Co-CEO/CTO of Calgary Scientific Inc., introduced you to the challenges, solutions and benefits of training AI systems to solve visual problems with an emphasis on improving AIs with continuous training in the field. He explored applications in several industries and discussed technologies that allow the deployment of advanced visualization solutions to the cloud.