Analysis and discussion of the open source data management project Cassandra. Related subjects include:
The 2013 Gartner Magic Quadrant for Operational Database Management Systems is out. “Operational” seems to be Gartner’s term for what I call short-request, in each case the point being that OLTP (OnLine Transaction Processing) is a dubious term when systems omit strict consistency, and when even strictly consistent systems may lack full transactional semantics. As is usually the case with Gartner Magic Quadrants:
- I admire the raw research.
- The opinions contained are generally reasonable (especially since Merv Adrian joined the Gartner team).
- Some of the details are questionable.
- There’s generally an excessive focus on Gartner’s perception of vendors’ business skills, and on vendors’ willingness to parrot all the buzzphrases Gartner wants to hear.
- The trends Gartner highlights are similar to those I see, although our emphasis may be different, and they may leave some important ones out. (Big omission — support for lightweight analytics integrated into operational applications, one of the more genuine forms of real-time analytics.)
Anyhow: Read more
Glassbeam checked in recently, and they turn out to exemplify quite a few of the themes I’ve been writing about. For starters:
- Glassbeam has an analytic technology stack focused on poly-structured machine-generated data.
- Glassbeam partially organizes that data into event series …
- … in a schema that is modified as needed.
Glassbeam basics include:
- Founded in 2009.
- Based in Santa Clara. Back-end engineering in Bangalore.
- $6 million in angel money; no other VC.
- High single-digit customer count, …
- … plus another high single-digit number of end customers for an OEM offering a limited version of their product.
All Glassbeam customers except one are SaaS/cloud (Software as a Service), and even that one was only offered a subscription (as oppose to perpetual license) price.
So what does Glassbeam’s technology do? Glassbeam says it is focused on “machine data analytics,” specifically for the “Internet of Things”, which it distinguishes from IT logs.* Specifically, Glassbeam sells to manufacturers of complex devices — IT (most of its sales so far ), medical, automotive (aspirational to date), etc. — and helps them analyze “phone home” data, for both support/customer service and marketing kinds of use cases. As of a recent release, the Glassbeam stack can: Read more
Hmm. I probably should have broken this out as three posts rather than one after all. Sorry about that.
Discussions of DBMS performance are always odd, for starters because:
- Workloads and use cases vary greatly.
- In particular, benchmarks such as the YCSB or TPC-H aren’t very helpful.
- It’s common for databases or at least working sets to be entirely in RAM — but it’s not always required.
- Consistency and durability models vary. What’s more, in some systems — e.g. MongoDB — there’s considerable flexibility as to which model you use.
- In particular, there’s an increasingly common choice in which data is written synchronously to RAM on 2 or more servers, then asynchronously to disk on each of them. Performance in these cases can be quite different from when all writes need to be committed to disk. Of course, you need sufficient disk I/O to keep up, so SSDs (Solid-State Drives) can come in handy.
- Many workloads are inherently single node (replication aside). Others are not.
MongoDB and 10gen
I caught up with Ron Avnur at 10gen. Technical highlights included: Read more
My clients at Couchbase checked in.
- After multiple delays, Couchbase 2.0 is well into beta, with general availability being delayed by the holiday season as much as anything else.
- Couchbase (the company) now has >350 subscription customers, almost all for Couchbase (the product) — which is to say for what was known as Membase, which is basically a persistent version of Memcached.
- There also are many users of open source Couchbase, most famously LinkedIn.
- Orbitz is a much-mentioned flagship paying Couchbase customer.
- Couchbase customers mainly seem to be replacing a caching layer, Memcached or otherwise.
- Couchbase headcount is just under 100.
The big changes in Couchbase 2.0 versus the previous (1.8.x) version are:
- JSON storage, including secondary indexes.
- Multi-data-center replication.
- A back-end change from SQLite to a heavily forked version of CouchDB, called Couchstore.
Couchbase 2.0 is upwards-compatible with prior versions of Couchbase (and hence with Memcached), but not with CouchDB.
Technology notes on Couchbase 2.0 include: Read more
|Categories: Basho and Riak, Cache, Cassandra, Clustering, Couchbase, MapReduce, Market share and customer counts, MongoDB, NoSQL, Open source, Structured documents||5 Comments|
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:
- Vanilla Cassandra.
- Cassandra plus Solr. Solr is a superset of the text-indexing system Lucene.
- Solr adds a lot more secondary indexing to Cassandra.
- In addition, these nodes serve as Solr emulation; you can run generic Solr apps on them.
- Cassandra plus Hadoop.
- You can use Hadoop MapReduce to manipulate generic Cassandra data.
- In addition, these nodes serve as Hadoop/HDFS (Hadoop Distributed File System) emulation; you can run generic Hadoop apps on them.
- Hadoop jobs can interweave access to the two kinds of data structure.
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:
- Cassandra is a column-group kind of NoSQL DBMS. You can get at its data programmatically.
- There’s something called CQL (Cassandra Query Language), said to be SQL-like.
- There’s a JDBC driver for CQL.
- With Hadoop MapReduce also come Hive, Pig, and Sqoop.
- With Solr and Lucene come full-text search.
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
|Categories: Cassandra, DataStax, Hadoop, MapReduce, Market share and customer counts, NoSQL, Open source, Text||6 Comments|
Edit: Multiple errors in the post below have been corrected in a follow-on post about DataStax Enterprise and Cassandra.
My client DataStax is announcing DataStax Enterprise 2.0. The big point of the release is that there’s a bunch of stuff integrated together, including at least:
- Cassandra — the NoSQL DBMS, which DataStax sometimes calls “DataStax Server”. Edit: That’s not really a fair criticism of DataStax’s messaging.
- Hadoop MapReduce, which DataStax sometimes calls “Hadoop”. Edit: That is indeed fair.
- Sqoop — the general way to connect relational DBMS to Hadoop, which DataStax sometimes calls “RDBMS integration”.
- Solr — the search-centric Apache project, or big parts of it, which DataStax generally calls either “Solr” or “Solr compatibility”.
- log4j – an Apache project that has something or other to do with logging, or parts of it, which DataStax sometimes calls “log file integration”.
- DataStax OpsCenter — some management tools and so on around Cassandra and the rest of the product line.
DataStax stresses that all this runs on the same cluster, with the same administrative tools and so on. For example, on a single cluster:
- You can manage the interactive data for a web site.
- You can store the logs for that website.
- You can analyze all of the above in Hadoop.
|Categories: Cassandra, Clustering, DataStax, EAI, EII, ETL, ELT, ETLT, Games and virtual worlds, Hadoop, Log analysis, Market share and customer counts, NoSQL, Parallelization, Text, Web analytics||5 Comments|
I checked in with James Phillips for a Couchbase update, and I understand better what’s going on. In particular:
- Give or take minor tweaks, what I wrote in my August, 2010 Couchbase updates still applies.
- Couchbase now and for the foreseeable future has one product line, called Couchbase.
- Couchbase 2.0, the first version of Couchbase (the product) to use CouchDB for persistence, has slipped …
- … because more parts of CouchDB had to be rewritten for performance than Couchbase (the company) had hoped.
- Think mid-year or so for the release of Couchbase 2.0, hopefully sooner.
- In connection with the need to rewrite parts of CouchDB, Couchbase has:
- Gotten out of the single-server CouchDB business.
- Donated its proprietary single-sever CouchDB intellectual property to the Apache Foundation.
- The 150ish new customers in 2011 Couchbase brags about are real, subscription customers.
- Couchbase has 60ish people, headed to >100 over the next few months.
|Categories: Basho and Riak, Cassandra, Couchbase, CouchDB, DataStax, Market share and customer counts, MongoDB, NoSQL, Open source, Parallelization, Web analytics, Zynga||6 Comments|
Recently, I observed that Big Data terminology is seriously broken. It is reasonable to reduce the subject to two quasi-dimensions:
- Bigness — Volume, Velocity, size
- Structure — Variety, Variability, Complexity
- High-velocity “big data” problems are usually high-volume as well.*
- Variety, variability, and complexity all relate to the simply-structured/poly-structured distinction.
But the conflation should stop there.
*Low-volume/high-velocity problems are commonly referred to as “event processing” and/or “streaming”.
When people claim that bigness and structure are the same issue, they oversimplify into mush. So I think we need four pieces of terminology, reflective of a 2×2 matrix of possibilities. For want of better alternatives, my suggestions are:
- Relational big data is data of high volume that fits well into a relational DBMS.
- Multi-structured big data is data of high volume that doesn’t fit well into a relational DBMS. Alternative: Poly-structured big data.
- Conventional relational data is data of not-so-high volume that fits well into a relational DBMS. Alternatives: Ordinary/normal/smaller relational data.
- Smaller poly-structured data is data for which dynamic schema capabilities are important, but which doesn’t rise to “big data” volume.
|Categories: Cassandra, Data models and architecture, Data warehousing, Exadata, Facebook, Google, Hadoop, HBase, Log analysis, Market share and customer counts, MarkLogic, NewSQL, NoSQL, Oracle, Splunk, Yahoo||10 Comments|
Last week I visited with James Phillips of Couchbase, Max Schireson and Eliot Horowitz of 10gen, and Todd Lipcon, Eric Sammer, and Omer Trajman of Cloudera. I guess it’s time for a round-up NoSQL post.
Views of the NoSQL market horse race are reasonably consistent, with perhaps some elements of “Where you stand depends upon where you sit.”
- As James tells it, NoSQL is simply a three-horse race between Couchbase, MongoDB, and Cassandra.
- Max would include HBase on the list.
- Further, Max pointed out that metrics such as job listings suggest MongoDB has the most development activity, and Couchbase/Membase/CouchDB perhaps have less.
- The Cloudera guys remarked on some serious HBase adopters.*
- Everybody I spoke with agreed that Riak had little current market presence, although some Basho guys could surely be found who’d disagree.
|Categories: Basho and Riak, Cassandra, Cloudera, Clustering, Couchbase, HBase, Market share and customer counts, MongoDB, NoSQL, Open source, Oracle, Parallelization||12 Comments|
A reporter tweeted: “Is there a simple plain English definition for NoSQL?” After reminding him of my cynical yet accurate Third Law of Commercial Semantics, I gave it a serious try, and came up with the following. More precisely, I tweeted the bolded parts of what’s below; the rest is commentary added for this post.
NoSQL is most easily defined by what it excludes: SQL, joins, strong analytic alternatives to those, and some forms of database integrity. If you leave all four out, and you have a strong scale-out story, you’re in the NoSQL mainstream. Read more
|Categories: Cassandra, dbShards and CodeFutures, MarkLogic, MySQL, Object, Open source, Petabyte-scale data management, Schooner Information Technology||7 Comments|