Welcome!

Linux Containers Authors: Elizabeth White, Liz McMillan, Zakia Bouachraoui, Yeshim Deniz, 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
Bill Schmarzo, Tech Chair of "Big Data | Analytics" of upcoming CloudEXPO | DXWorldEXPO New York (November 12-13, 2018, New York City) today announced the outline and schedule of the track. "The track has been designed in experience/degree order," said Schmarzo. "So, that folks who attend the entire track can leave the conference with some of the skills necessary to get their work done when they get back to their offices. It actually ties back to some work that I'm doing at the University of San...
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...
When talking IoT we often focus on the devices, the sensors, the hardware itself. The new smart appliances, the new smart or self-driving cars (which are amalgamations of many ‘things'). When we are looking at the world of IoT, we should take a step back, look at the big picture. What value are these devices providing. IoT is not about the devices, its about the data consumed and generated. The devices are tools, mechanisms, conduits. This paper discusses the considerations when dealing with the...
Bill Schmarzo, author of "Big Data: Understanding How Data Powers Big Business" and "Big Data MBA: Driving Business Strategies with Data Science," is responsible for setting the strategy and defining the Big Data service offerings and capabilities for EMC Global Services Big Data Practice. As the CTO for the Big Data Practice, he is responsible for working with organizations to help them identify where and how to start their big data journeys. He's written several white papers, is an avid blogge...
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...
If a machine can invent, does this mean the end of the patent system as we know it? The patent system, both in the US and Europe, allows companies to protect their inventions and helps foster innovation. However, Artificial Intelligence (AI) could be set to disrupt the patent system as we know it. This talk will examine how AI may change the patent landscape in the years to come. Furthermore, ways in which companies can best protect their AI related inventions will be examined from both a US and...
Enterprises have taken advantage of IoT to achieve important revenue and cost advantages. What is less apparent is how incumbent enterprises operating at scale have, following success with IoT, built analytic, operations management and software development capabilities - ranging from autonomous vehicles to manageable robotics installations. They have embraced these capabilities as if they were Silicon Valley startups.
Chris Matthieu is the President & CEO of Computes, inc. He brings 30 years of experience in development and launches of disruptive technologies to create new market opportunities as well as enhance enterprise product portfolios with emerging technologies. His most recent venture was Octoblu, a cross-protocol Internet of Things (IoT) mesh network platform, acquired by Citrix. Prior to co-founding Octoblu, Chris was founder of Nodester, an open-source Node.JS PaaS which was acquired by AppFog and ...
The deluge of IoT sensor data collected from connected devices and the powerful AI required to make that data actionable are giving rise to a hybrid ecosystem in which cloud, on-prem and edge processes become interweaved. Attendees will learn how emerging composable infrastructure solutions deliver the adaptive architecture needed to manage this new data reality. Machine learning algorithms can better anticipate data storms and automate resources to support surges, including fully scalable GPU-c...
Cloud-enabled transformation has evolved from cost saving measure to business innovation strategy -- one that combines the cloud with cognitive capabilities to drive market disruption. Learn how you can achieve the insight and agility you need to gain a competitive advantage. Industry-acclaimed CTO and cloud expert, Shankar Kalyana presents. Only the most exceptional IBMers are appointed with the rare distinction of IBM Fellow, the highest technical honor in the company. Shankar has also receive...