Best data store for billions of rows

Question

I need to be able to store small bits of data (approximately 50-75 bytes) for billions of records (~3 billion/month for a year).

The only requirement is fast inserts and fast lookups for all records with the same GUID and the ability to access the data store from .net.

I'm a SQL server guy and I think SQL Server can do this, but with all the talk about BigTable, CouchDB, and other nosql solutions, it's sounding more and more like an alternative to a traditional RDBS may be best due to optimizations for distributed queries and scaling. I tried cassandra and the .net libraries don't currently compile or are all subject to change (along with cassandra itself).

I've looked into many nosql data stores available, but can't find one that meets my needs as a robust production-ready platform.

If you had to store 36 billion small, flat records so that they're accessible from .net, what would choose and why?

Thulium

Yeah, my numbers are correct. Currently we have this much data coming into the system, but we aggregate it and store only the aggregate counts so we lose the per-record data and maintain only hourly sums of data. Due to business requirements, we want to maintain each record as it originally occurred and that's 3Bil rows/month. – Thulium

You've raised some good questions. The answers are: 95% up time is enough - the data is already delayed a variable amount so I'll need to sync it up after the fact anyway so being down for a short time isn't a deal breaker. Losing inserts or even thousands of inserts aren't the end of the world. Losing a day's worth of data would be pretty bad though. Consistency isn't that important either. Basically after inserting 30Mil rows in a day, I need to fetch all the rows with the same GUID (maybe 20 rows) and be reasonably sure I'd get them all back. – Thulium

Do you dump 30M rows a day in daily/hourly scheduled batch jobs, or they come in a constant flux one at a time? – Assumptive

The data arrives from an FTP site... files come in continuously and I have a process that parses the files and currently it generates the aggregated data and inserts the aggregated values (maybe 1000 rows) as a transaction. The new process will need to insert hundreds of thousands of rows from each file that arrives, probably using bulk insert would be the most efficient way to do it. – Thulium

That sounds like an ETL job for SSIS and SQL Server. They do hold a world record for ETL, at over 2TB/hour upload speed: blogs.msdn.com/sqlperf/archive/2008/02/27/etl-world-record.aspx – Assumptive

Answer 1

Storing ~3.5TB of data and inserting about 1K/sec 24x7, and also querying at a rate not specified, it is possible with SQL Server, but there are more questions:

• what availability requirement you have for this? 99.999% uptime, or is 95% enough?
• what reliability requirement you have? Does missing an insert cost you $1M?
• what recoverability requirement you have? If you loose one day of data, does it matter?
• what consistency requirement you have? Does a write need to be guaranteed to be visible on the next read?

If you need all these requirements I highlighted, the load you propose is going to cost millions in hardware and licensing on an relational system, any system, no matter what gimmicks you try (sharding, partitioning etc). A nosql system would, by their very definition, not meet all these requirements.

So obviously you have already relaxed some of these requirements. There is a nice visual guide comparing the nosql offerings based on the 'pick 2 out of 3' paradigm at Visual Guide to NoSQL Systems:

After OP comment update

With SQL Server this would e straight forward implementation:

• one single table clustered (GUID, time) key. Yes, is going to get fragmented, but is fragmentation affect read-aheads and read-aheads are needed only for significant range scans. Since you only query for specific GUID and date range, fragmentation won't matter much. Yes, is a wide key, so non-leaf pages will have poor key density. Yes, it will lead to poor fill factor. And yes, page splits may occur. Despite these problems, given the requirements, is still the best clustered key choice.
• partition the table by time so you can implement efficient deletion of the expired records, via an automatic sliding window. Augment this with an online index partition rebuild of the last month to eliminate the poor fill factor and fragmentation introduced by the GUID clustering.
• enable page compression. Since the clustered key groups by GUID first, all records of a GUID will be next to each other, giving page compression a good chance to deploy dictionary compression.
• you'll need a fast IO path for log file. You're interested in high throughput, not on low latency for a log to keep up with 1K inserts/sec, so stripping is a must.

Partitioning and page compression each require an Enterprise Edition SQL Server, they will not work on Standard Edition and both are quite important to meet the requirements.

As a side note, if the records come from a front-end Web servers farm, I would put Express on each web server and instead of INSERT on the back end, I would SEND the info to the back end, using a local connection/transaction on the Express co-located with the web server. This gives a much much better availability story to the solution.

So this is how I would do it in SQL Server. The good news is that the problems you'll face are well understood and solutions are known. that doesn't necessarily mean this is a better than what you could achieve with Cassandra, BigTable or Dynamo. I'll let someone more knowleageable in things no-sql-ish to argument their case.

Note that I never mentioned the programming model, .Net support and such. I honestly think they're irrelevant in large deployments. They make huge difference in the development process, but once deployed it doesn't matter how fast the development was, if the ORM overhead kills performance :)

Assumptive

I hot linked Nathan's site, but this is not slashdot front page ;) – Assumptive

@RemusRusanu: looking at dba.se migration. Just to prepare you :-) And +1 – Mucus

As of Microsoft SQL Server 2016, Enterprise edition is no longer required for Table Partitioning as Table Partitioning is now available in almost all editions of SQL Server 2016. – Illusory

Answer 2

Contrary to popular belief, NoSQL is not about performance, or even scalability. It's mainly about minimizing the so-called Object-Relational impedance mismatch, but is also about horizontal scalability vs. the more typical vertical scalability of an RDBMS.

For the simple requirement of fasts inserts and fast lookups, almost any database product will do. If you want to add relational data, or joins, or have any complex transactional logic or constraints you need to enforce, then you want a relational database. No NoSQL product can compare.

If you need schemaless data, you'd want to go with a document-oriented database such as MongoDB or CouchDB. The loose schema is the main draw of these; I personally like MongoDB and use it in a few custom reporting systems. I find it very useful when the data requirements are constantly changing.

The other main NoSQL option is distributed Key-Value Stores such as BigTable or Cassandra. These are especially useful if you want to scale your database across many machines running commodity hardware. They work fine on servers too, obviously, but don't take advantage of high-end hardware as well as SQL Server or Oracle or other database designed for vertical scaling, and obviously, they aren't relational and are no good for enforcing normalization or constraints. Also, as you've noticed, .NET support tends to be spotty at best.

All relational database products support partitioning of a limited sort. They are not as flexible as BigTable or other DKVS systems, they don't partition easily across hundreds of servers, but it really doesn't sound like that's what you're looking for. They are quite good at handling record counts in the billions, as long as you index and normalize the data properly, run the database on powerful hardware (especially SSDs if you can afford them), and partition across 2 or 3 or 5 physical disks if necessary.

If you meet the above criteria, if you're working in a corporate environment and have money to spend on decent hardware and database optimization, I'd stick with SQL Server for now. If you're pinching pennies and need to run this on low-end Amazon EC2 cloud computing hardware, you'd probably want to opt for Cassandra or Voldemort instead (assuming you can get either to work with .NET).

Firecrest

Answer 3

Very few people work at the multi-billion row set size, and most times that I see a request like this on stack overflow, the data is no where near the size it is being reported as.

36 billion, 3 billion per month, thats roughly 100 million per day, 4.16 million an hour, ~70k rows per minute, 1.1k rows a second coming into the system, in a sustained manner for 12 months, assuming no down time.

Those figures are not impossible by a long margin, i've done larger systems, but you want to double check that is really the quantities you mean - very few apps really have this quantity.

In terms of storing / retrieving and quite a critical aspect you have not mentioned is aging the older data - deletion is not free.

The normal technology is look at is partitioning, however, the lookup / retrieval being GUID based would result in a poor performance, assuming you have to get every matching value across the whole 12 month period. You could place a clustered indexes on the GUID column will get your associated data clusterd for read / write, but at those quantities and insertion speed, the fragmentation will be far too high to support, and it will fall on the floor.

I would also suggest that you are going to need a very decent hardware budget if this is a serious application with OLTP type response speeds, that is by some approximate guesses, assuming very few overheads indexing wise, about 2.7TB of data.

In the SQL Server camp, the only thing that you might want to look at is the new parrallel data warehouse edition (madison) which is designed more for sharding out data and running parallel queries against it to provide high speed against large datamarts.

Gaily

In bioinformatics billion-row datasets are not uncommon. But they are frequently dealt with in a purely streaming fashion from flat files. – Chekiang

@Erik: for stream processing (ie. just need to detect certain conditions, but there is no need to store the data for later querying) something like StreamInsight is better than any database microsoft.com/sqlserver/2008/en/us/r2-complex-event.aspx – Assumptive

Answer 4

"I need to be able to store small bits of data (approximately 50-75 bytes) for billions of records (~3 billion/month for a year).

The only requirement is fast inserts and fast lookups for all records with the same GUID and the ability to access the data store from .net."

I can tell you from experience that this is possible in SQL Server, because I have done it in early 2009 ... and it's still operation to this day and quite fast.

The table was partitioned in 256 partitions, keep in mind this was 2005 SQL version ... and we did exactly what you're saying, and that is to store bits of info by GUID and retrieve by GUID quickly.

When i left we had around 2-3 billion records, and data retrieval was still quite good (1-2 seconds if get through UI, or less if on RDBMS) even though the data retention policy was just about to be instantiated.

So, long story short, I took the 8th char (i.e. somewhere in the middle-ish) from the GUID string and SHA1 hashed it and cast as tiny int (0-255) and stored in appropriate partition and used same function call when getting the data back.

ping me if you need more info...

Agrostology

Answer 5

The following article discusses the import and use of a 16 billion row table in Microsoft SQL. https://www.itprotoday.com/big-data/adventures-big-data-how-import-16-billion-rows-single-table.

From the article:

Here are some distilled tips from my experience:

• The more data you have in a table with a defined clustered index, the slower it becomes to import unsorted records into it. At some point, it becomes too slow to be practical.
• If you want to export your table to the smallest possible file, make it native format. This works best with tables containing mostly numeric columns because they’re more compactly represented in binary fields than character data. If all your data is alphanumeric, you won’t gain much by exporting it in native format. Not allowing nulls in the numeric fields can further compact the data. If you allow a field to be nullable, the field’s binary representation will contain a 1-byte prefix indicating how many bytes of data will follow.
• You can’t use BCP for more than 2,147,483,647 records because the BCP counter variable is a 4-byte integer. I wasn’t able to find any reference to this on MSDN or the Internet. If your table consists of
  more than 2,147,483,647 records, you’ll have to export it in chunks
  or write your own export routine.
• Defining a clustered index on a prepopulated table takes a lot of disk space. In my test, my log exploded to 10 times the original
  table size before completion.
• When importing a large number of records using the BULK INSERT statement, include the BATCHSIZE parameter and specify how many
  records to commit at a time. If you don’t include this parameter,
  your entire file is imported as a single transaction, which
  requires a lot of log space.
• The fastest way of getting data into a table with a clustered index is to presort the data first. You can then import it using the BULK
  INSERT statement with the ORDER parameter.

Deming

I edited the link. But the Internet Archive failed to import the new link so when it breaks next time, it might be for good. – Photomechanical

Answer 6

There is an unusual fact that seems to overlooked.

"Basically after inserting 30Mil rows in a day, I need to fetch all the rows with the same GUID (maybe 20 rows) and be reasonably sure I'd get them all back"

Needing only 20 columns, a non-clustered index on the GUID will work just fine. You could cluster on another column for data dispersion across partitions.

I have a question regarding the data insertion: How is it being inserted?

• Is this a bulk insert on a certain schedule (per min, per hour, etc)?
• What source is this data being pulled from (flat files, OLTP, etc)?

I think these need to be answered to help understand one side of the equation.

Gleich

Answer 7

Amazon Redshift is a great service. It was not available when the question was originally posted in 2010, but it is now a major player in 2017. It is a column based database, forked from Postgres, so standard SQL and Postgres connector libraries will work with it.

It is best used for reporting purposes, especially aggregation. The data from a single table is stored on different servers in Amazon's cloud, distributed by on the defined table distkeys, so you rely on distributed CPU power.

So SELECTs and especially aggregated SELECTs are lightning fast. Loading large data should be preferably done with the COPY command from Amazon S3 csv files. The drawbacks are that DELETEs and UPDATEs are slower than usual, but that is why Redshift in not primarily a transnational database, but more of a data warehouse platform.

Semi

Answer 8

You can try using Cassandra or HBase, though you would need to read up on how to design the column families as per your use case. Cassandra provides its own query language but you need to use Java APIs of HBase to access the data directly. If you need to use Hbase then I recommend querying the data with Apache Drill from Map-R which is an Open Source project. Drill's query language is SQL-Compliant(keywords in drill have the same meaning they would have in SQL).

Adne

Answer 9

With that many records per year you're eventually going to run out of space. Why not filesystem storage like xfs which supports 2^64 files and using smaller boxes. Regardless of how fancy people want to get or the amount of money one would end up spend getting a system with whatever database SQL NoSQL ..whichever these many records are usually made by electric companies and weather stations/providers like ministry of environment who control smaller stations throughout the country. If you're doing something like storing pressure.. temperature..wind speed.. humidity etc...and guid is the location..you can still divide the data by year/month/day/hour. Assuming you store 4 years of data per hard-drive. You can then have it run on a smaller Nas with mirror where it would also provide better read speeds and have multiple mount points..based on the year when it was created. You can simply make a web-interface for searches So dumping location1/2001/06/01//temperature and location1/2002/06/01//temperature would only dump the contents of hourly temperature for the 1st day of summer in those 2 years (24h*2) 48 small files vs searching a database with billions of records and possibly millions spent. Simple way of looking at things.. 1.5 billion websites in the world with God knows how many pages each If a company like Google had to spend millions per 3 billion searches to pay for super-computers for this they'd be broke. Instead they have the power-bill...couple million crap computers. And caffeine indexing...future-proof..keep adding more. And yeah where indexing running off SQL makes sense then great Building super-computers for crappy tasks with fixed things like weather...statistics and so on so techs can brag their systems crunches xtb in x seconds...waste of money that can be spent somewhere else..maybe that power-bill that won't run into the millions anytime soon by running something like 10 Nas servers.

Aleenaleetha

Answer 10

Store records in plain binary files, one file per GUID, wouldn't get any faster than that.

Exsert

Do you really expect this to perform well? – Macroscopic

Yea, creating billions of files on file system can be devastating to some file systems. I made the mistake of doing something like this, but with only 1 million and I pretty much took the system down trying to open a shell to one of those folders. Also, unless you are looking up based on a guid, how is the query mechanism supposed to work? – Birdhouse

It is hard to guess how this would perform without knowing how many unique GUID's are expected :) But is doesn't get any simpler than just writing to plain files. And fast inserts along with lookup by GUID was the only requirement. – Brookes

It can work but you have to limit the number of files per folder. You have to generate a new folder per n files. You could use a substring of the guid as folder name. – Mcmorris

FaceBook uses a database based on ... flat files in a disk hierarchy. It definitely works. When you are storing files in a hierarchy, its almost infinitely scalable with no loss of speed, as long as you don't store more than a few thousand files per directory. – Flinders

yes, there is a limit on the number of inodes for lots of filesystems and I remember hitting that limit ourselves on redhat default filesystem....the limit was around 1,000,000 files or so. – Middling

Would want to make sure there is no concurrent access either. – Brufsky

Answer 11

You can use MongoDB and use the guid as the sharding key, this means that you can distribute your data over multiple machines but the data you want to select is only on one machine because you select by the sharding key.

Sharding in MongoDb is not yet production ready.

Astrolabe