MapReduce

Analysis of implementations of and issues associated with the parallel programming framework MapReduce. Related subjects include:

June 19, 2012

Notes on HBase 0.92

This is part of a four-post series, covering:

As part of my recent round of Hadoop research, I talked with Cloudera’s Todd Lipcon. Naturally, one of the subjects was HBase, and specifically HBase 0.92. I gather that the major themes to HBase 0.92 are:

HBase coprocessors are Java code that links straight into HBase. As with other DBMS extensions of the “links straight into the DBMS code” kind,* HBase coprocessors seem best suited for very sophisticated users and third parties.** Evidently, coprocessors have already been used to make HBase security more granular — role-based, per-column-family/per-table, etc. Further, Todd thinks coprocessors could serve as a good basis for future HBase enhancements in areas such as aggregation or secondary indexing. Read more

June 19, 2012

“Enterprise-ready Hadoop”

This is part of a four-post series, covering:

The posts depend on each other in various ways.

Cloudera, Hortonworks, and MapR all claim, in effect, “Our version of Hadoop is enterprise-ready, unlike those other guys’.” I’m dubious.

That said, “enterprise-ready Hadoop” really is an important topic.

So what does it mean for something to be “enterprise-ready”, in whole or in part? Common themes in distinguishing between “enterprise-class” and other software include:

For Hadoop, as for most things, these concepts overlap in many ways. Read more

June 19, 2012

Hadoop distributions: CDH 4, HDP 1, Hadoop 2.0, Hadoop 1.0 and all that

This is part of a four-post series, covering:

The posts depend on each other in various ways.

My clients at Cloudera and Hortonworks have somewhat different views as to the maturity of various pieces of Hadoop technology. In particular:

*”CDH” stands, due to some trademarking weirdness, for “Cloudera’s Distribution including Apache Hadoop”. “HDP” stands for “Hortonworks Data Platform”.

Read more

June 3, 2012

Introduction to Cloudant

Cloudant is one of the few NoSQL companies with >100 paying subscription customers. For starters:

Company demographics include:

The Cloudant guys gave me some customer counts in May that weren’t much higher than those they gave me in February, and seem to have forgotten to correct the discrepancy. Oh well. The latter (probably understated) figures included ~160 paying customers, of which:

The largest Cloudant deployments seem to be in the 10s of terabytes, across a very low double digit number of servers.

Read more

May 13, 2012

Notes on the analysis of large graphs

This post is part of a series on managing and analyzing graph data. Posts to date include:

My series on graph data management and analytics got knocked off-stride by our website difficulties. Still, I want to return to one interesting set of issues — analyzing large graphs, specifically ones that don’t fit comfortably into RAM on a single server. By no means do I have the subject figured out. But here are a few notes on the matter.

How big can a graph be? That of course depends on:

*Even if your graph has 10 billion nodes, those can be tokenized in 34 bits, so the main concern is edges. Edges can include weights, timestamps, and so on, but how many specifics do you really need? At some point you can surely rely on a pointer to full detail stored elsewhere.

The biggest graph-size estimates I’ve gotten are from my clients at Yarcdata, a division of Cray. (“Yarc” is “Cray” spelled backwards.) To my surprise, they suggested that graphs about people could have 1000s of edges per node, whether in:

Yarcdata further suggested that bioinformatics use cases could have node counts higher yet, characterizing Bio2RDF as one of the “smaller” ones at 22 billion nodes. In these cases, the nodes/edge average seems lower than in people-analysis graphs, but we’re still talking about 100s of billions of edges.

Recalling that relationship analytics boils down to finding paths and subgraphs, the naive relational approach to such tasks would be: Read more

April 24, 2012

Notes on the Hadoop and HBase markets

I visited my clients at Cloudera and Hortonworks last week, along with scads of other companies. A few of the takeaways were:

March 27, 2012

DataStax Enterprise and Cassandra revisited

My last post about DataStax Enterprise and Cassandra didn’t go so well. As follow-up, I chatted for two hours with Rick Branson and Billy Bosworth of DataStax. Hopefully I can do better this time around.

For starters, let me say there are three kinds of data management nodes in DataStax Enterprise:

Cassandra, Solr, Lucene, and Hadoop are all Apache projects.

If we look at this from the standpoint of DML (Data Manipulation Language) and data access APIs:

In addition, it is sometimes recommended that you use “in-entity caching”, where an entire data structure (e.g. in JSON) winds up in a single Cassandra column.

The two main ways to get direct SQL* access to data in DataStax Enterprise are:

*or very SQL-like, depending on how you view things

Before going further, let’s recall some Cassandra basics: Read more

March 12, 2012

Kinds of data integration and movement

“Data integration” can mean many different things, to an extent that’s impeding me from writing about the area. So I’ll start by simply laying out some of the myriad ways that data can be brought to where it is needed, and worry about other subjects later. Yes, this is a massive wall of text, and incomplete even so — but that in itself is my central point.

There are two main paradigms for data integration:

Data movement and replication typically take one of three forms:

Beyond the core functions of movement, replication, and/or federation, there are other concerns closely connected to data integration. These include:

In particular, the following are largely different from each other. Read more

February 7, 2012

Hadoop-related market categorization

I wasn’t the only one to be dubious about Forrester Research’s Hadoop taxonomy (or lack thereof). GigaOm’s Derrick Harris was as well, and offered a much superior approach of his own. In Derrick’s view, there’s Hadoop, Hadoop distributions, Hadoop management, and Hadoop applications. Taking those out of order, and recalling that no market categorization is ever precise:

Let’s drill down into that last one. Derrick refers to Hadoop distributions as “products” that:

package a set of Hadoop projects (MapReduce, Hive, Sqoop, Pig, etc.) in a way that in theory makes them integrate more naturally, and to run both smoothly and securely.

While that’s a reasonable recitation of the idea’s benefits, I’d rather say that a “distribution” of open source software comprises: Read more

February 6, 2012

Comments on the 2012 Forrester Wave: Enterprise Hadoop Solutions

Forrester has released its Q1 2012 Forrester Wave: Enterprise Hadoop Solutions. (Googling turns up a direct link, but in case that doesn’t prove stable, here also is a registration-required link from IBM’s Conor O’Mahony.) My comments include:

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