Theory and architecture
Analysis of design choices in databases and database management systems. Related subjects include:
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MongoDB users and use cases
I spoke with Eliot Horowitz and Max Schierson of 10gen last month about MongoDB users and use cases. The biggest clusters they came up with weren’t much over 100 nodes, but clusters an order of magnitude bigger were under development. The 100 node one we talked the most about had 33 replica sets, each with about 100 gigabytes of data, so that’s in the 3-4 terabyte range total. In general, the largest MongoDB databases are 20-30 TB; I’d guess those really do use the bulk of available disk space. Read more
| Categories: Data models and architecture, Games and virtual worlds, Log analysis, MongoDB, NoSQL, Solid-state memory, Specific users, Splunk, Telecommunications, Web analytics | 13 Comments |
HBase is not broken
It turns out that my impression that HBase is broken was unfounded, in at least two ways. The smaller is that something wrong with the HBase/Hadoop interface or Hadoop’s HBase support cannot necessarily be said to be wrong with HBase (especially since HBase is no longer a Hadoop subproject). The bigger reason is that, according to consensus, HBase has worked pretty well since the .90 release in January of this year.
After Michael Stack of StumbleUpon beat me up for a while,* Omer Trajman of Cloudera was kind enough to walk me through HBase usage. He is informed largely by 18 Cloudera customers, plus a handful of other well-known HBase users such as Facebook, StumbleUpon, and Yahoo. Of the 18 Cloudera customers using HBase that Omer was thinking of, 15 are in HBase production, one is in HBase “early production”, one is still doing R&D in the area of HBase, and one is a classified government customer not providing such details. Read more
| Categories: Cloudera, Derived data, Facebook, Hadoop, HBase, Log analysis, Market share and customer counts, Open source, Specific users, Web analytics | 6 Comments |
Soundbites: the Facebook/MySQL/NoSQL/VoltDB/Stonebraker flap, continued
As a follow-up to the latest Stonebraker kerfuffle, Derrick Harris asked me a bunch of smart followup questions. My responses and afterthoughts include:
- Facebook et al. are in effect Software as a Service (SaaS) vendors, not enterprise technology users. In particular:
- They have the technical chops to rewrite their code as needed.
- Unlike packaged software vendors, they’re not answerable to anybody for keeping legacy code alive after a rewrite. That makes migration a lot easier.
- If they want to write different parts of their system on different technical underpinnings, nobody can stop them. For example …
- … Facebook innovated Cassandra, and is now heavily committed to HBase.
- It makes little sense to talk of Facebook’s use of “MySQL.” Better to talk of Facebook’s use of “MySQL + memcached + non-transparent sharding.” That said:
- It’s hard to see why somebody today would use MySQL + memcached + non-transparent sharding for a new project. At least one of Couchbase or transparently-sharded MySQL is very likely a superior alternative. Other alternatives might be better yet.
- As noted above in the example of Facebook, the many major web businesses that are using MySQL + memcached + non-transparent sharding for existing projects can be presumed able to migrate away from that stack as the need arises.
Continuing with that discussion of DBMS alternatives:
- If you just want to write to the memcached API anyway, why not go with Couchbase?
- If you want to go relational, why not go with MySQL? There are many alternatives for scaling or accelerating MySQL — dbShards, Schooner, Akiban, Tokutek, ScaleBase, ScaleDB, Clustrix, and Xeround come to mind quickly, so there’s a great chance that one or more will fit your use case. (And if you don’t get the choice of MySQL flavor right the first time, porting to another one shouldn’t be all THAT awful.)
- If you really, really want to go in-memory, and don’t mind writing Java stored procedures, and don’t need to do the kinds of joins it isn’t good at, but do need to do the kinds of joins it is, VoltDB could indeed be a good alternative.
And while we’re at it — going schema-free often makes a whole lot of sense. I need to write much more about the point, but for now let’s just say that I look favorably on the Big Four schema-free/NoSQL options of MongoDB, Couchbase, HBase, and Cassandra.
An odd claim attributed to Mike Stonebraker
This post has a sequel.
Last week, Mike Stonebraker insulted MySQL and Facebook’s use of it, by implication advocating VoltDB instead. Kerfuffle ensued. To the extent Mike was saying that non-transparently sharded MySQL isn’t an ideal way to do things, he’s surely right. That still leaves a lot of options for massive short-request databases, however, including transparently sharded RDBMS, scale-out in-memory DBMS (whether or not VoltDB*), and various NoSQL options. If nothing else, Couchbase would seem superior to memcached/non-transparent MySQL if you were starting a project today.
*The big problem with VoltDB, last I checked, was its reliance on Java stored procedures to get work done.
Pleasantries continued in The Register, which got an amazing-sounding quote from Mike. If The Reg is to be believed — something I wouldn’t necessarily take for granted — Mike claimed that he (i.e. VoltDB) knows how to solve the distributed join performance problem. Read more
| Categories: Cache, Clustering, Couchbase, Games and virtual worlds, In-memory DBMS, memcached, Michael Stonebraker, MySQL, Parallelization, Theory and architecture, VoltDB and H-Store | 20 Comments |
Sybase IQ soundbites
Sybase made a total hash of the timing of this week’s press release. I got annoyed after they promised to inform me of the new embargo time, then broke the promise. Other people got annoyed earlier than that.
So be it. Below is the draft of a post I was holding, with brackets added around one word that is no longer accurate.
I don’t write enough about Sybase IQ. That said, I offered a couple of quotes to a reporter [yesterday] in connection with the general availability of Sybase IQ 15.3. Lightly edited, they go:
- “Shared-everything MPP” isn’t a total contradiction in terms. It’s great for adding in concurrent users. And there’s little doubt that Sybase IQ can support robust access to databases 10s of terabytes in size.
- As I first noted a couple of years ago, virtual data marts are a good idea. Too few vendors are making it easy to spin them out. They let departments start doing analytics very quickly, yet allow IT to keep partial control.
Beyond that, I should note:
- Sybase IQ is the classic choice for what I call traditional data marts.
- Sybase IQ is a leader in temporal functionality, which is not coincidental to its presence in the financial services market.
| Categories: Columnar database management, Data warehousing, Parallelization, Sybase, Theory and architecture | Leave a Comment |
Hadapt update
I met with the Hadapt guys today. I think I can be a bit crisper than before in positioning Hadapt and its use cases, namely:
- Hadapt is additional software on a cluster that also runs fully functional Hadoop/HDFS. (Cloudera Hadoop more than straight-from-Apache Hadoop to date, but that’s not a requirement.)
- The cluster also runs a DBMS on every node, such as PostgreSQL or one of Infobright/Vectorwise.
- Hadapt’s software manages parallel SQL queries by distributing them to the DBMS living on each node. Hadapt says that the resulting query performance far outshines Hive’s.
- Hadapt further says that, by exploiting the partner DBMS, its SQL functionality outpaces Hive’s as well.
- Target Hadapt use cases are centered around keeping machine-generated or other poly-structured data in Hadoop, and extracting, enhancing, or otherwise deriving some of it to live in the relational store.
- In particular, Hadapt seems like an interesting choice when you want to use that relational data as you work on other data that’s still in HDFS, or if you want to keep using the relational data in other kinds of MapReduce jobs.
- That all fits well with my thoughts about the importance of derived data.
Other evolution from what I wrote about Hadapt a few months ago includes:
- Hadapt is in beta now.
- Hadapt has added adult supervision in the form of Philip Wickline, late of Endeca.
In other news, Hadapt is our newest client.
Petabyte-scale Hadoop clusters (dozens of them)
I recently learned that there are 7 Vertica clusters with a petabyte (or more) each of user data. So I asked around about other petabyte-scale clusters. It turns out that there are several dozen such clusters (at least) running Hadoop.
Cloudera can identify 22 CDH (Cloudera Distribution [of] Hadoop) clusters holding one petabyte or more of user data each, at 16 different organizations. This does not count Facebook or Yahoo, who are huge Hadoop users but not, I gather, running CDH. Meanwhile, Eric Baldeschwieler of Hortonworks tells me that Yahoo’s latest stated figures are:
- 42,000 Hadoop nodes …
- … holding 180-200 petabytes of data.
Hadoop hardware and compression
A month ago, I posted about typical Hadoop hardware. After talking today with Eric Baldeschwieler of Hortonworks, I have an update. I also learned some things from Eric and from Brian Christian of Zettaset about Hadoop compression.
First the compression part. Eric thinks 6-10X compression is common for “curated” Hadoop data — i.e., the data that actually gets used a lot. Brian used an overall figure of 6-8X, and told of a specific customer who had 6X or a little more. By way of comparison, it sounds as if the kinds of data involved are like what Vertica claimed 10-60X compression for almost three years ago.
Eric also made an excellent point about low-value machine-generated data. I was suggesting that as Moore’s Law made sensor networks ever more affordable: Read more
| Categories: Cloudera, Database compression, Hadoop, Hortonworks, Storage, Vertica Systems, Zettaset | 10 Comments |
Eight kinds of analytic database (Part 2)
In Part 1 of this two-part series, I outlined four variants on the traditional enterprise data warehouse/data mart dichotomy, and suggested what kinds of DBMS products you might use for each. In Part 2 I’ll cover four more kinds of analytic database — even newer, for the most part, with a use case/product short list match that is even less clear. Read more
Eight kinds of analytic database (Part 1)
Analytic data management technology has blossomed, leading to many questions along the lines of “So which products should I use for which category of problem?” The old EDW/data mart dichotomy is hopelessly outdated for that purpose, and adding a third category for “big data” is little help.
Let’s try eight categories instead. While no categorization is ever perfect, these each have at least some degree of technical homogeneity. Figuring out which types of analytic database you have or need — and in most cases you’ll need several — is a great early step in your analytic technology planning. Read more