Jeff Kolesky describing the data model they are using with HBase and one (strange) trick to reduce the roundtrips to the database:

The idea is to put all of the data about a single entity into a single row in HBase. When you need to run a computation that involves that entity’s data, you have quick access to it by the row key, and all of the data is stored close together on disk.

Additionally, against many suggestions from the HBase community, and general confusion about how timestamps work, we are using timestamps with logical values. Instead of just letting the region server assign a timestamp version to each cell, we are explicitly setting those values so that we can use timestamp as a true queryable dimension in our gets and scans.

In addition to the real timeseries data that is indexed using the cell timestamp, we also have other columns that store metadata about the entity.

It’s amazing how many smart and weird tricks engineers put in their production systems when having to deal with real requirements and SLAs.

Original title and link: HBase Data Modeling Tips & Tricks - Timeshifting (NoSQL database©myNoSQL)

via: http://www.heyitsopower.com/code/timeshifting-in-hbase/

Ben Bromhead (instaclustr) for High Scalability:

To determine the suitability of a provider, your first port of call is to benchmark. Choosing a service provider is often done in a number of stages. First is to shortlist providers based on capabilities and claimed performance, ruling out those that do not meet your application requirements. Second is to look for benchmarks conducted by third parties, if any. The final stage is to benchmark the service yourself.

✚ Peter Bailis asks a very valid question: if it’s the default YCSB and it’s a benchmark, where are the results?”

✚ instaclustr offers a totally managed hosting solution for Cassandra. (Disclaimer: they’ve sponsored myNoSQL in the past)

Original title and link: 5 Steps to Benchmarking Managed NoSQL - DynamoDB Vs Cassandra (NoSQL database©myNoSQL)

via: http://highscalability.com/blog/2013/4/3/5-steps-to-benchmarking-managed-nosql-dynamodb-vs-cassandra.html

Sam Tunnicliffe’s describes the old and new, optimized behavior of secondary indexes writes in Cassandra 1.2:

While secondary indexes can add a lot of flexibility to the way data is modelled and accessed, they do add complexity on the server side as the indexes need to be kept in sync with the primary data. Until recently, this has led to some significant trade offs in write throughput and IO utilisation as we always had to perform a read before the write in order to update any relevant secondary indexes. In Cassandra 1.2, this area has been substantially reworked to remove the need for read-before-write. New index entries are now written at the same time as the primary data is updated and old entries removed lazily at query time. Overall, this has lead to some decent performance improvements.

Original title and link: Improving Secondary Index Write Performance in Cassandra 1.2 (NoSQL database©myNoSQL)

via: http://www.datastax.com/dev/blog/improving-secondary-index-write-performance-in-1-2

Ted Yu summarizes some of the most frequent questions related to compactions in HBase:

On user mailing list, questions about compaction are probably the most frequently asked.

Original title and link: HBase Compactions Q&A (NoSQL database©myNoSQL)

via: http://zhihongyu.blogspot.com/2013/03/compactions-q.html

This RSS reader app from Netflix can be a very good excuse to use Cassandra, some of the open source projects from Netflix and why not create an alternative to Google’s Reader which is declared defunct or alive every couple of months:

Projects you’ll use: Cassandra with Astyanax, Archaius, Blitz4j, Eurka, Governator, Hystrix, Karyon, Ribbon, Servo. As for myself, I’ve already checked out the code.

Original title and link: RSS Reader With Cassandra and Netflix OSS Tools (NoSQL database©myNoSQL)

via: http://techblog.netflix.com/2013/03/introducing-first-netflixoss-recipe-rss.html

Matteo Bertozzi introduces HBase snapshots:

Prior to CDH 4.2, the only way to back-up or clone a table was to use Copy/Export Table, or after disabling the table, copy all the hfiles in HDFS. Copy/Export Table is a set of tools that uses MapReduce to scan and copy the table but with a direct impact on Region Server performance. Disabling the table stops all reads and writes, which will almost always be unacceptable.

In contrast, HBase snapshots allow an admin to clone a table without data copies and with minimal impact on Region Servers. Exporting the snapshot to another cluster does not directly affect any of the Region Servers; export is just a distcp with an extra bit of logic.

The part that made me really curious and that didn’t make too much sense when first reading the post is “clone a table without data copies”. But the post clarifies what the snapshot is:

A snapshot is a set of metadata information that allows an admin to get back to a previous state of the table. A snapshot is not a copy of the table; it’s just a list of file names and doesn’t copy the data. A full snapshot restore means that you get back to the previous “table schema” and you get back your previous data losing any changes made since the snapshot was taken.

What I still don’t understand is how snapshots are working after a major compaction (which drops deletes and expired cells).

Original title and link: Introduction to Apache HBase Snapshots (NoSQL database©myNoSQL)

via: http://blog.cloudera.com/blog/2013/03/introduction-to-apache-hbase-snapshots/

Jon Natkins from WibiData:

When building an HBase application, you need to be aware of the intricacies and quirks of HBase. For example, your choice of names for column families, or columns themselves can have a drastic effect on the amount of disk space necessary to store your data. In this article, we’ll see how building HBase applications with KijiSchema can help you avoid inefficient disk utilization.

The recommendations related to the length of column names is a one of those subtle signs of how young the NoSQL space is¹.

Original title and link: Simplifying HBase Schema Development With KijiSchema (NoSQL database©myNoSQL)

via: http://www.kiji.org/2012/03/01/using-disk-space-efficiently-with-kiji-schema