Welcome!

Linux Containers Authors: Yeshim Deniz, Liz McMillan, Zakia Bouachraoui, Elizabeth White, Pat Romanski

Related Topics: Linux Containers, Open Source Cloud, Recurring Revenue

Linux Containers: Article

Proactively Preventing Data Corruption

Linux gains end-to-end data integrity protection

Data Integrity Extensions
  • Allow transfer of data integrity information to and from the host operating system
  • Allow separation of data and integrity metadata buffers
  • Allow a lightweight checksum algorithm to limit impact on operating system performance

I/O Controller Data Integrity Extensions
While the increased resilience against errors between controller and storage device is an improvement, the design goal was to enable true end-to-end data integrity protection. An obvious approach was to expose the DIF information above the I/O controller level and let the operating system gain access to the integrity metadata.

Buffer Separation
There were a few problems with exposing the 520-byte sectors to the OS, however. Internally, operating systems generally work with sizes that are multiples of 512. On x86 and x86_64 hardware, the system page size is 4096 KB. This means that 8 sectors fit nicely in a page. It’s extremely inconvenient for the operating system to deal with buffers that are multiples of 520 bytes.

The Data Integrity Extensions allow the operating system to gain access to the DIF content without changing its internal buffer size. This is achieved by separating the data buffers and the integrity metadata buffers. The controller firmware will interleave the data and integrity buffers on write and split them on read.

Separating the data from the integrity metadata in the operating system also reduces the risk of data corruption. Now two buffers in different locations need to match up for an I/O request to be successfully completed.

Performance Implications
The DIF protection between I/O controller and disk is handled by custom hardware at near zero performance penalty. For true end-to-end data integrity, however, the application or the operating system needs to generate the protection information. Calculating the checksum in software obviously comes at a performance penalty and the T10 DIF standard mandates a heavyweight 16-bit CRC algorithm for the guard tag.

This CRC is quite expensive to calculate compared to other commonly used checksums. To alleviate the impact on system performance the TCP/IP checksum algorithm is used instead. This results in an almost negligible impact on system performance. The Data Integrity Extensions allow this alternate checksum type to be used by the operating system. The I/O controller will convert the IP checksum to the T10 DIF CRC when sending a request to the storage device and vice versa.

The net result is that a full end-to-end protection envelope can be provided at a very low cost in terms of processing overhead.

Linux Data Integrity Framework
Oracle has implemented support for DIF and the I/O Controller Data Integrity Extensions in the Linux kernel. The changes are released under the GNU General Public License and have been submitted for inclusion in the official kernel tree. With this, Linux becomes the first operating system to gain true end-to-end data integrity protection.

  • Allows integrity metadata to be attached to an I/O request
  • Allows filesystems to use the application tag for added recoverability
  • Allows integrity metadata to be generated automatically for unmodified applications
  • Will allow advanced applications to manually send and receive integrity metadata

The Linux changes allow integrity metadata to be generated and passed through the I/O stack. Currently the extensions are only accessible from within the kernel, but a userland API is in development. The goal is for all applications to be able to benefit from the extra data protection features.

At a recent Storage Networking industry conference, Oracle and its partners demonstrated an (unmodified) Oracle database running on Linux using the data integrity framework. The server used a prototype Emulex fibre channel controller, a disk tray from LSI, and disk drives from Seagate. We demonstrated how errors could be injected into the system, identified, isolated, and remedied without causing downtime or on-disk corruption.

The SCSI standard only governs communications between the I/O controller and storage device, and as such the interface between I/O controller and the operating system is outside the scope of the T10 organization. Consequently, Oracle and its partners have approached the Storage Networking Industry Association and set up Data Integrity Task Force with the intent to standardize the data integrity interfaces for applications, operating systems and I/O controllers.

Hardware products supporting DIF and the I/O Controller Data Integrity Extensions are scheduled for release in 2008.

Relevant Links

More Stories By Martin Petersen

Martin K. Petersen has been involved in Linux development since the early nineties. He has worked on PA-RISC and IA-64 Linux ports for HP as well as the XFS filesystem and the Altix kernel for SGI. Martin works in Oracle's Linux Engineering group where he focuses on enterprise storage technologies.

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.


IoT & Smart Cities Stories
Dion Hinchcliffe is an internationally recognized digital expert, bestselling book author, frequent keynote speaker, analyst, futurist, and transformation expert based in Washington, DC. He is currently Chief Strategy Officer at the industry-leading digital strategy and online community solutions firm, 7Summits.
Digital Transformation is much more than a buzzword. The radical shift to digital mechanisms for almost every process is evident across all industries and verticals. This is often especially true in financial services, where the legacy environment is many times unable to keep up with the rapidly shifting demands of the consumer. The constant pressure to provide complete, omnichannel delivery of customer-facing solutions to meet both regulatory and customer demands is putting enormous pressure on...
IoT is rapidly becoming mainstream as more and more investments are made into the platforms and technology. As this movement continues to expand and gain momentum it creates a massive wall of noise that can be difficult to sift through. Unfortunately, this inevitably makes IoT less approachable for people to get started with and can hamper efforts to integrate this key technology into your own portfolio. There are so many connected products already in place today with many hundreds more on the h...
The standardization of container runtimes and images has sparked the creation of an almost overwhelming number of new open source projects that build on and otherwise work with these specifications. Of course, there's Kubernetes, which orchestrates and manages collections of containers. It was one of the first and best-known examples of projects that make containers truly useful for production use. However, more recently, the container ecosystem has truly exploded. A service mesh like Istio addr...
Digital Transformation: Preparing Cloud & IoT Security for the Age of Artificial Intelligence. As automation and artificial intelligence (AI) power solution development and delivery, many businesses need to build backend cloud capabilities. Well-poised organizations, marketing smart devices with AI and BlockChain capabilities prepare to refine compliance and regulatory capabilities in 2018. Volumes of health, financial, technical and privacy data, along with tightening compliance requirements by...
Charles Araujo is an industry analyst, internationally recognized authority on the Digital Enterprise and author of The Quantum Age of IT: Why Everything You Know About IT is About to Change. As Principal Analyst with Intellyx, he writes, speaks and advises organizations on how to navigate through this time of disruption. He is also the founder of The Institute for Digital Transformation and a sought after keynote speaker. He has been a regular contributor to both InformationWeek and CIO Insight...
Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life settlement products to hedge funds and investment banks. After, he co-founded a revenue cycle management company where he learned about Bitcoin and eventually Ethereal. Andrew's role at ConsenSys Enterprise is a mul...
To Really Work for Enterprises, MultiCloud Adoption Requires Far Better and Inclusive Cloud Monitoring and Cost Management … But How? Overwhelmingly, even as enterprises have adopted cloud computing and are expanding to multi-cloud computing, IT leaders remain concerned about how to monitor, manage and control costs across hybrid and multi-cloud deployments. It’s clear that traditional IT monitoring and management approaches, designed after all for on-premises data centers, are falling short in ...
In his general session at 19th Cloud Expo, Manish Dixit, VP of Product and Engineering at Dice, discussed how Dice leverages data insights and tools to help both tech professionals and recruiters better understand how skills relate to each other and which skills are in high demand using interactive visualizations and salary indicator tools to maximize earning potential. Manish Dixit is VP of Product and Engineering at Dice. As the leader of the Product, Engineering and Data Sciences team at D...
Dynatrace is an application performance management software company with products for the information technology departments and digital business owners of medium and large businesses. Building the Future of Monitoring with Artificial Intelligence. Today we can collect lots and lots of performance data. We build beautiful dashboards and even have fancy query languages to access and transform the data. Still performance data is a secret language only a couple of people understand. The more busine...