TheStraightTech: How are Distribution and Replication Related?

If you use GlusterFS, you know that there are several types of volumes you can create:

  • Distributed – Distributes files throughout the bricks in the volume.
  • Replicated – Replicates files across bricks in the volume.
  • Striped – Stripes data across bricks in the volume.
  • Distributed Striped – Distributes data across striped bricks in the volume.
  • Distributed Replicated – Distributes files across replicated bricks in the volume.

In GlusterFS, unlike most similar systems, these two types of data-placement decisions are kept completely separate.  Distribution, which places each file in exactly one place for the purpose of aggregating capacity within a single namespace, is provided by the DHT translator.  Replication, which places each file in N places for improved availability, is provided by the AFR translator.

The relationship between DHT and AFR can be viewed from two opposite perspectives – the configuration order and the execution order.  If you hear someone refer to “distribute-first” or “replicate-first” that generally refers to the configuration order.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s