Archive for August, 2009

21
Aug
By Aster in Blogroll, nPath on August 21, 2009
   

John Cieslewicz, Eric Friedman, and Peter Pawlowski of Aster Data Systems

This post was co-authored by John Cieslewicz, Eric Friedman, and Peter Pawlowski of Aster Data Systems

One year ago we introduced SQL/MapReduce for the Aster nCluster database, which integrates MapReduce and SQL to enable deep analytics within the database. Pushing computation inside the database and close to the data is increasingly important as data sizes grow exponentially. As SQL/MR turns one year old, we are happy to announce that we will be presenting our SQL/MR innovations next week at the 35th International Conference on Very Large Data Bases (VLDB), the premier international forum for database research.

The title of our conference paper is SQL/MapReduce: A Practical Approach to Self-describing, Polymorphic, and Parallelizable User-defined Functions. The title of the paper may be large, but so are the advanced analytics possibilities created by the invention of SQL/MR!

We developed SQL/MR because we saw a growing gap between the deep analytics and application needs of very large data and the capabilities provided by SQL and traditional relational-only data processing. We call this gap, the “SQL Gap.”

The SQL Gap

SQL and the relational query processing model are well suited for many, but not all data processing tasks. Some queries are cumbersome, non-intuitive or impossible to express in SQL (note: now that SQL is turing complete, nothing is strictly impossible, but it can be very painful and perform very badly) - check out our paper for some examples. Moreover, query optimizers have a limited number of algorithms at their disposal to process data, which leads to convoluted data processing in situations where applying a little domain knowledge can yield a much more straightforward algorithm.

We found traditional user-defined functions (UDFs) to fall short in bridging this gap between SQL and the answers to challenging analytic problems that need to be solved. UDFs are often user-unfriendly, inflexible, and not easily parallelized. SQL/MR functions, in contrast, are designed to be easy to develop, easy to install, and easy to use - providing developers and analysts with a powerful tool to tackle the challenges posed by very large data.

To do this, we integrated the MapReduce programming model with SQL. MapReduce is a well known paradigm for parallel, fault-tolerant data processing that allows developers to write procedural code that is then applied to data in parallel. Pure MapReduce, however, misses out on aspects of SQL and relational data processing that are great - such as query optimizations, managed data, and transactions. By integrating SQL and MapReduce on top of Aster nCluster’s hardware management and fault tolerance, we leverage the strengths of each, resulting in a system that is much more powerful than either in isolation.

SQL/MapReduce At VLDB
SQL/MR is much more than a user-defined function. As our paper title states, a SQL/MR function is self-describing, polymorphic, and parallelizable. Let’s explore each of these characteristics and see why we hope researchers at VLDB will be as excited as we are by SQL/MR.

Self-Describing and Polymorphic
The behavior and output characteristics of a SQL/MR function are determined dynamically at query-time instead of statically at install-time as is the case with traditional user-defined functions. These characteristics allow SQL/MR functions to behave much more like general purpose library functions than single-use, specific application user-defined functions. When a SQL/MR function is used in a query, the nCluster query planner negotiates a contract with the SQL/MR function, providing the function’s input schema and optional user-supplied parameters. In return, the SQL/MR function agrees to a contract that specifies its output schema for the duration of the query. This contract negotiation is what makes SQL/MR functions self-describing, and their ability to be invoked on different input with different optional parameters makes them polymorphic as well. To summarize, by invoking a SQL/MR function on different input, with different optional parameters, the SQL/MR function may export a different output schema and perform different computation - the possibilities are entirely up to the developer!

Parallelizable
The SQL/MR programming model, like that of MapReduce, is inherently parallelizable. Developers write procedural code in the language of their choice, but at runtime that code will run in parallel across hundreds of nodes within an nCluster database. Advanced analytics and application code can now be executed in parallel, directly on data stored within nCluster making nCluster an application-friendly, high performance data warehouse and data application system. Advanced analytics capabilities that we have already pushed inside nCluster using SQL/MR include click-stream sessionization, general purpose time series path matching, dynamic and massively parallel data loading from heterogeneous sources, and genetic sequence analysis.

Bridging the Gap
SQL/MapReduce has matured greatly over the past year and is used by our customers in creative ways we never imagined - proof positive that SQL/MapReduce is an effective way to bridge the “SQL Gap” to deeper analytics on very large data. Check out the other application examples and sample code videos on www.asterdata.com, as well as the MapReduce category of this blog

We’d love to hear from you about any type of analysis you’re doing where stand-alone SQL is becoming overly-complex … and please look us up at the VLDB 2009 show if you’re making the trip to Lyon, France!

(Apart from the authors, Brent Chun, Mohit Aron, Abhishek Marwah, Raghu Venkat, Vinay Bondhugula, and Prasan Roy of Aster Data Systems are notable contributors to the overall SQL/MR effort.)



03
Aug
Netezza’s Change in Architecture - Move towards Commodity
By Mayank Bawa in Blogroll, TCO on August 3, 2009
   

Netezza pre-announced last week that they will be moving to a new architecture - one based around IBM blades (Linux + Intel + RAM) with commodity SAS disks, RAID controllers, and NICs. The product will continue to rely on an FPGA, but that would sit much further from the disks & RAID controller, beyond the RAM but adjacent to the Intel CPU, in contrast to their previous product line.

In assembling a new hardware stack, Netezza calls this re-architecture as a change but not really a change - the FPGA will continue to offload data compression/decompression, selection and projection from the Intel CPU; the Intel CPU will be used to push-down joins and group bys; the RAM will be used to enable caching (thus helping improve mixed workload performance).

I think this is a pretty significant change for Netezza.

Clearly, Netezza would not have invested in this change - assemble & ship a new hardware stack to share revenue with IBM vs. a 3rd party hardware assembler - if Netezza’s old FPGA-dominant hardware was not being out-priced and out-performed by our Intel-based commodity hardware.

It was a matter of time before the market realized that FPGA’s had reached their end-of-life status in the data warehousing market. In realizing the writing on the wall, and responding to it early, Netezza has made a bold decision to change - and yet, clung to the warm familiarity of an FPGA as a “side car”.

Netezza, and the rest of the market, will soon become aware that a change in hardware stack is not a free lunch. The richness of CPU and RAM resources in an IBM commodity blade come at a cost that a resource-starved FPGA-based architecture never had to account for.

In 2009, after having engineered its software for an FPGA over the last 9 years, Netezza will need to come to terms with commodity hardware in production systems and demonstrate that they can:

- Manage processes and memory spawned by a single query across 100s of blade servers

- Maintain consistent caches across 100s of blade servers - after all, it is Oracle’s Cache Fusion technology that is the bane of scaling Oracle RAC beyond 8 blade servers

- Tolerate the higher frequency of failures that a commodity Linux + RAID Controller/driver + Network driver stack incur when put under rigorous data movement (e.g., allocation/de-allocation of memory contributing to memory leaks)

- Add a new IBM blade and ensure incremental scaling of their appliance

- Upgrade the software stack in place - unlike an FPGA-based hardware stack that customers are OK to floor-sweep in their upgrade

- Contain run-away queries from allocating the abundant CPU and RAM resources and starving other concurrent queries in the workload

- Reduce network traffic for a blade with 2 NICs that is managing 8 disks vs. a Power-PC/FPGA that had 1 NIC for 1 disk

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If you take a quick pulse of the market, apart from our known installations of 100+ servers, there is no other vendor - mature or new-age - who has demonstrated that 100′s of commodity servers can be made to work together to run a single database.

And I believe that there is a fundamental reason for this lack of proof-point even a decade after Linux has matured and commodity servers have been used for computing - software not built from the ground-up to leverage the richness and contain the limitations of commodity hardware is incapable of scaling. Aster nCluster has been built ground up to have these capabilities on a commodity stack. Netezza’s software written for proprietary hardware cannot be retrofitted to work on commodity hardware (else, Netezza would have completely taken the FPGAs out, now that they have powerful CPUs!). Netezza has its work cut-out - they have taken a dramatic shift that has the ability to bring the company and its production customers to its knees. And there-in lies Netezza’s challenge - they must succeed while supporting their current customers on an FPGA-based platform while moving resources to build out a commodity-based platform.

And we have not even touched upon the extension of SQL with MapReduce to power big data manipulation using arbitrary user-written procedures.

If a system is not fundamentally designed to leverage commodity servers, it’s only going to be a band-aid on seams that are bursting. Overall, we will curiously watch how long it takes Netezza to eliminate their FPGAs completely and move to a real commodity stack so that the customers can have the freedom to choose their own hardware and not be locked down to Netezza-supplied custom hardware.