Analysis of technology that compresses data within a database management system. Related subjects include:
- Question: Why do policemen work in pairs?
- Answer: One to read and one to write.
A lot has happened in MongoDB technology over the past year. For starters:
- The big news in MongoDB 3.0* is the WiredTiger storage engine. The top-level claims for that are that one should “typically” expect (individual cases can of course vary greatly):
- 7-10X improvement in write performance.
- No change in read performance (which however was boosted in MongoDB 2.6).
- ~70% reduction in data size due to compression (disk only).
- ~50% reduction in index size due to compression (disk and memory both).
- MongoDB has been adding administration modules.
- A remote/cloud version came out with, if I understand correctly, MongoDB 2.6.
- An on-premise version came out with 3.0.
- They have similar features, but are expected to grow apart from each other over time. They have different names.
*Newly-released MongoDB 3.0 is what was previously going to be MongoDB 2.8. My clients at MongoDB finally decided to give a “bigger” release a new first-digit version number.
To forestall confusion, let me quickly add: Read more
|Categories: Database compression, Hadoop, Humor, In-memory DBMS, MongoDB and 10gen, NoSQL, Open source, Structured documents, Sybase||7 Comments|
I have a small blacklist of companies I won’t talk with because of their particularly unethical past behavior. Actian is one such; they evidently made stuff up about me that Josh Berkus gullibly posted for them, and I don’t want to have conversations that could be dishonestly used against me.
That said, Peter Boncz isn’t exactly an Actian employee. Rather, he’s the professor who supervised Marcin Zukowski’s PhD thesis that became Vectorwise, and I chatted with Peter by Skype while he was at home in Amsterdam. I believe his assurances that no Actian personnel sat in on the call.
In other news, Peter is currently working on and optimistic about HyPer. But we literally spent less than a minute talking about that
Before I get to the substance, there’s been a lot of renaming at Actian. To quote Andrew Brust,
… the ParAccel, Pervasive and Vectorwise technologies are being unified under the Actian Analytics Platform brand. Specifically, the ParAccel technology … is being re-branded Actian Matrix; Pervasive’s technologies are rechristened Actian DataFlow and Actian DataConnect; and Vectorwise becomes Actian Vector.
Actian … is now “one company, with one voice and one platform” according to its John Santaferraro
The bolded part of the latter quote is untrue — at least in the ordinary sense of the word “one” — but the rest can presumably be taken as company gospel.
All this is by way of preamble to saying that Peter reached out to me about Actian’s new Vector Hadoop Edition when he blogged about it last June, and we finally talked this week. Highlights include: Read more
|Categories: Actian and Ingres, Clustering, Database compression, Hadoop, ParAccel, Pervasive Software, SQL/Hadoop integration, VectorWise, Workload management||4 Comments|
One of my lesser-known clients is Citus Data, a largely Turkish company that is however headquartered in San Francisco. They make CitusDB, which puts a scale-out layer over a collection of fully-functional PostgreSQL nodes, much like Greenplum and Aster Data before it. However, in contrast to those and other Postgres-based analytic MPP (Massively Parallel Processing) DBMS:
- CitusDB does not permanently fork PostgreSQL; Citus Data has committed to always working with the latest PostgreSQL release, or at least with one that’s less than a year old.
- Citus Data never made the “fat head” mistake — if a join can’t be executed directly on the CitusDB data-storing nodes, it can’t be executed in CitusDB at all.
- CitusDB follows the modern best-practice of having many virtual nodes on each physical node. Default size of a virtual node is one gigabyte. Each virtual node is technically its own PostgreSQL table.*
- Citus Data has already introduced an open source column-store option for PostgreSQL, which CitusDB of course exploits.
*One benefit to this strategy, besides the usual elasticity and recovery stuff, is that while PostgreSQL may be single-core for any given query, a CitusDB query can use multiple cores by virtue of hitting multiple PostgreSQL tables on each node.
Citus has thrown a few things against the wall; for example, there are two versions of its product, one which involves HDFS (Hadoop Distributed File System) and one of which doesn’t. But I think Citus’ focus will be scale-out PostgreSQL for at least the medium-term future. Citus does have actual customers, and they weren’t all PostgreSQL users previously. Still, the main hope — at least until the product is more built-out — is that existing PostgreSQL users will find CitusDB easy to adopt, in technology and price alike.
|Categories: Aster Data, Citus Data, Columnar database management, Data warehousing, Database compression, Greenplum, Hadoop, Parallelization, PostgreSQL, SQL/Hadoop integration, Transparent sharding, Workload management||6 Comments|
I stopped by MemSQL last week, and got a range of new or clarified information. For starters:
- Even though MemSQL (the product) was originally designed for OLTP (OnLine Transaction Processing), MemSQL (the company) is now focused on analytic use cases …
- … which was the point of introducing MemSQL’s flash-based columnar option.
- One MemSQL customer has a 100 TB “data warehouse” installation on Amazon.
- Another has “dozens” of terabytes of data spread across 500 machines, which aggregate 36 TB of RAM.
- At customer Shutterstock, 1000s of non-MemSQL nodes are monitored by 4 MemSQL machines.
- A couple of MemSQL’s top references are also Vertica flagship customers; one of course is Zynga.
- MemSQL reports encountering Clustrix and VoltDB in a few competitive situations, but not NuoDB. MemSQL believes that VoltDB is still hampered by its traditional issues — Java, reliance on stored procedures, etc.
On the more technical side: Read more
|Categories: Clustering, Clustrix, Columnar database management, Data warehousing, Database compression, In-memory DBMS, MemSQL, NewSQL, NuoDB, Specific users, Vertica Systems, VoltDB and H-Store, Workload management, Zynga||18 Comments|
I caught up with my clients at MongoDB to discuss the recent MongoDB 2.6, along with some new statements of direction. The biggest takeaway is that the MongoDB product, along with the associated MMS (MongoDB Management Service), is growing up. Aspects include:
- An actual automation and management user interface, as opposed to the current management style, which is almost entirely via scripts (except for the monitoring UI).
- That’s scheduled for public beta in May, and general availability later this year.
- It will include some kind of integrated provisioning with VMware, OpenStack, et al.
- One goal is to let you apply database changes, software upgrades, etc. without taking the cluster down.
- A reasonable backup strategy.
- A snapshot copy is made of the database.
- A copy of the log is streamed somewhere.
- Periodically — the default seems to be 6 hours — the log is applied to create a new current snapshot.
- For point-in-time recovery, you take the last snapshot prior to the point, and roll forward to the desired point.
- A reasonable locking strategy!
- Document-level locking is all-but-promised for MongoDB 2.8.
- That means what it sounds like. (I mention this because sometimes an XML database winds up being one big document, which leads to confusing conversations about what’s going on.)
- Security. My eyes glaze over at the details, but several major buzzwords have been checked off.
- A general code rewrite to allow for (more) rapid addition of future features.
Memory-centric data management is confusing. And so I’m going to clarify a couple of things about MemSQL 3.0 even though I don’t yet have a lot of details.* They are:
- MemSQL has historically been an in-memory row store, which as of last year scales out.
- It turns out that the MemSQL row store actually has two table types. One is scaled out. The other — called “reference” — is replicated on every node.
- MemSQL has now added a third table type, which is columnar and which resides in flash memory.
- If you want to keep data in, for example, both the scale-out row store and the column store, you’d have to copy/replicate it within MemSQL. And if you wanted to access data from both versions at once (e.g. because different copies cover different time periods), you’d likely have to do a UNION or something like that.
*MemSQL’s first columnar offering sounds pretty basic; for example, there’s no columnar compression yet. (Edit: Oops, that’s not accurate. See comment below.) But at least they actually have one, which puts them ahead of many other row-based RDBMS vendors that come to mind.
And to hammer home the contrast:
- IBM, Oracle and Microsoft, which all sell row-based DBMS meant to run on disk or other persistent storage, have added or will add columnar options that run in RAM.
- MemSQL, which sells a row-based DBMS that runs in RAM, has added a columnar option that runs in persistent solid-state storage.
|Categories: Columnar database management, Database compression, In-memory DBMS, MemSQL, Solid-state memory||12 Comments|
The general Tokutek strategy has always been:
- Write indexes efficiently, which …
- … makes it reasonable to have more indexes, which …
- … lets more queries run fast.
But the details of “writes indexes efficiently” have been hard to nail down. For example, my post about Tokutek indexing last January, while not really mistaken, is drastically incomplete.
Adding further confusion is that Tokutek now has two product lines:
- TokuDB, a MySQL storage engine.
- TokuMX, in which the parts of MongoDB 2.2 that roughly equate to a storage engine are ripped out and replaced with Tokutek code.
TokuMX further adds language support for transactions and a rewrite of MongoDB’s replication code.
So let’s try again. I had a couple of conversations with Martin Farach-Colton, who:
- Is a Tokutek co-founder.
- Stayed in academia.
- Is a data structures guy, not a database expert per se.
The core ideas of Tokutek’s architecture start: Read more
I chatted yesterday with the Hortonworks gang. The main subject was Hortonworks’ approach to SQL-on-Hadoop — commonly called Stinger — but at my request we cycled through a bunch of other topics as well. Company-specific notes include:
- Hortonworks founder J. Eric “Eric14″ Baldeschwieler is no longer at Hortonworks, although I imagine he stays closely in touch. What he’s doing next is unspecified, except by the general phrase “his own thing”. (Derrick Harris has more on Eric’s departure.)
- John Kreisa still is at Hortonworks, just not as marketing VP. Think instead of partnerships and projects.
- ~250 employees.
- ~70-75 subscription customers.
Our deployment and use case discussions were a little confused, because a key part of Hortonworks’ strategy is to support and encourage the idea of combining use cases and workloads on a single cluster. But I did hear:
- 10ish nodes for a typical starting cluster.
- 100ish nodes for a typical “data lake” committed adoption.
- Teradata UDA (Unified Data Architecture)* customers sometimes (typically?) jumping straight to a data lake scenario.
- A few users in the 10s of 1000s of nodes. (Obviously Yahoo is one.)
- HBase used in >50% of installations.
- Hive probably even more than that.
- Hortonworks is seeing a fair amount of interest in Windows Hadoop deployments.
*By the way — Teradata seems serious about pushing the UDA as a core message.
Ecosystem notes, in Hortonworks’ perception, included:
- Cloudera is obviously Hortonworks’ biggest distro competitor. Next is IBM, presumably in its blue-forever installed base. MapR is barely on the radar screen; Pivotal’s likely rise hasn’t yet hit sales reports.
- Hortonworks evidently sees a lot of MicroStrategy and Tableau, and some Platfora and Datameer, the latter two at around the same level of interest.
- Accumulo is a big deal in the Federal government, and has gotten a few health care wins as well. Its success is all about security. (Note: That’s all consistent with what I hear elsewhere.)
I also asked specifically about OpenStack. Hortonworks is a member of the OpenStack project, contributes nontrivially to Swift and other subprojects, and sees Rackspace as an important partner. But despite all that, I think strong Hadoop/OpenStack integration is something for the indefinite future.
Hortonworks’ views about Hadoop 2.0 start from the premise that its goal is to support running a multitude of workloads on a single cluster. (See, for example, what I previously posted about Tez and YARN.) Timing notes for Hadoop 2.0 include:
- It’s been in preview/release candidate/commercial beta mode for weeks.
- Q3 is the goal; H2 is the emphatic goal.
- Yahoo’s been in production with YARN >8 months, and has no MapReduce 1 clusters left. (Yahoo has >35,000 Hadoop nodes.)
- The last months of delays have been mainly about sprucing up various APIs and protocols, which may need to serve for a similar multi-year period as Hadoop 1’s have. But there also was some YARN stabilization into May.
Frankly, I think Cloudera’s earlier and necessarily incremental Hadoop 2 rollout was a better choice than Hortonworks’ later big bang, even though the core-mission aspect of Hadoop 2.0 is what was least ready. HDFS (Hadoop Distributed File System) performance, NameNode failover and so on were well worth having, and it’s more than a year between Cloudera starting supporting them and when Hortonworks is offering Hadoop 2.0.
Hortonworks’ approach to doing SQL-on-Hadoop can be summarized simply as “Make Hive into as good an analytic RDBMS as possible, all in open source”. Key elements include: Read more
I visited Cloudera Friday for, among other things, a chat about Impala with Marcel Kornacker and colleagues. Highlights included:
- Impala is meant to someday be a competitive MPP (Massively Parallel Processing) analytic RDBMS.
- At the moment, it is not one. For example, Impala lacks any meaningful form of workload management or query optimization.
- While Impala will run against any HDFS (Hadoop Distributed File System) file format, claims of strong performance assume that the data is in Parquet …
- … which is the replacement for the short-lived Trevni …
- … and which for most practical purposes is true columnar.
- Impala is also meant to be more than an RDBMS; Parquet and presumably in the future Impala can accommodate nested data structures.
- Just as Impala runs against most or all HDFS file formats, Parquet files can be used by most Hadoop execution engines, and of course by Pig and Hive.
- The Impala roadmap includes workload management, query optimization, data skipping, user-defined functions, hash distribution, two turtledoves, and a partridge in a pear tree.
Data gets into Parquet via batch jobs only — one reason it’s important that Impala run against multiple file formats — but background format conversion is another roadmap item. A single table can be split across multiple formats — e.g., the freshest data could be in HBase, with the rest is in Parquet.
I had a good chat with IBM about IBM BLU, aka BLU Accelerator or Acceleration. BLU basics start:
- BLU is a part of DB2.
- BLU works like a columnar analytic DBMS.
- If you want to do a join combining BLU and non-BLU tables, all the BLU tables are joined first, and the result set is joined to the other tables by the rest of DB2.
And yes — that means Oracle is now the only major relational DBMS vendor left without a true columnar story.
BLU’s maturity and scalability basics start:
- BLU is coming out in IBM DB2 10.5, this quarter.
- BLU will initially be single-server, but …
- … IBM claims “near-linear” scalability up to 64 cores, and further says that …
- … scale-out for BLU is coming “soon”.
- IBM already thinks all your analytically-oriented DB2 tables should be in BLU.
- IBM describes the first version of BLU as being optimized for 10 TB databases, but capable of handling 20 TB.
BLU technical highlights include: Read more
|Categories: Columnar database management, Data pipelining, Data warehousing, Database compression, IBM and DB2, Workload management||20 Comments|