Feeds

Google open sources MapReduce compression

In the name of speed

Providing a secure and efficient Helpdesk

Google has open sourced the compression library used across its backend infrastructure, including MapReduce, its distributed number-crunching platform, and BigTable, its distributed database.

Available at Google Code under an Apache 2.0 license, the library is called Snappy, but Google says this is the same library that was previously referred to as Zippy in some public presentations. As the names imply, the library's primary aim is speed. "It does not aim for maximum compression, or compatibility with any other compression library," Google says. "Instead, it aims for very high speeds and reasonable compression."

Compared to the fastest mode of the popular zlib compression library, Google says, the C++-based Snappy is an order of magnitude faster in most cases (roughly ten times faster), but the compressed files are between 20 and 100 per cent larger. Running in 64-bit mode on a single core of a 2.26Ghz "Westmere" Intel Core i7 processor, according to the company, Snappy compresses at roughly 250MB/sec and decompresses at 500MB/sec.

Google says that the typical compression ratios are about 1.5x to 1.7x for plain text and about 2x to 4x for HTML. zlib in its fastest mode gives you 2.6x to 2.8x for plain text and 3x to 7x for HTML. " So if you want to save space, or want to compress once and decompress lots of times, use zlib (or bzip2, or…). But if you just want to cut down on your I/O, be it network or disk I/O, Snappy might be for you," says Google engineer Steinar Gunderson.

According to Gunderson, Snappy removes the "entropy reduction" step that characterizes zlib and other LZ-style compression libraries. "Most LZ-style compressors (including zlib) consist of two parts: A matching algorithm (recognizing repetitions from data earlier in the stream, as well as things like 'abcabcabcabc') and then an entropy reduction step (almost invariably Huffman or some version of arithmetic encoding)," he says. "Snappy skips the entropy reduction and instead uses a fixed, hand-tuned packing format."

This format, Gunderson says, affords "much less" CPU usage, and he says that Google has spent years fine tuning it. Virtually all of Google's online service run atop a uniform distributed infrastructure based on the proprietary Google File System (GFS), MapReduce, BigTable, and other platforms. This have been mimicked in the open source world by the Apache Hadoop project. ®

Beginner's guide to SSL certificates

More from The Register

next story
ONE MILLION people already running Windows 10
A third of them are doing it in VMs, but early feedback focuses on frippery
Netscape Navigator - the browser that started it all - turns 20
It was 20 years ago today, Marc Andreeesen taught the band to play
Sign off my IT project or I’ll PHONE your MUM
Honestly, it’s a piece of piss
Sway: Microsoft's new Office app doesn't have an Undo function
Content aggregation, meet the workplace ... oh
Do Moan! MONSTER 6-day EMAIL OUTAGE hits Domain Monster
Customers freaked out by frightful service
Ploppr: The #VultureTRENDING App of the Now
This organic crowd sourced viro- social fertiliser just got REAL
Return of the Jedi – Apache reclaims web server crown
.london, .hamburg and .公司 - that's .com in Chinese - storm the web server charts
NetWare sales revive in China thanks to that man Snowden
If it ain't Microsoft, it's in fashion behind the Great Firewall
prev story

Whitepapers

Forging a new future with identity relationship management
Learn about ForgeRock's next generation IRM platform and how it is designed to empower CEOS's and enterprises to engage with consumers.
Win a year’s supply of chocolate
There is no techie angle to this competition so we're not going to pretend there is, but everyone loves chocolate so who cares.
Why cloud backup?
Combining the latest advancements in disk-based backup with secure, integrated, cloud technologies offer organizations fast and assured recovery of their critical enterprise data.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?
Saudi Petroleum chooses Tegile storage solution
A storage solution that addresses company growth and performance for business-critical applications of caseware archive and search along with other key operational systems.