[Gluster-devel] Dispersed volume: Initial results

[Xavier Hernandez]

Hi all,

I've been able to do the first performance comparison of a dispersed 
volume. The translators still have known problems that will be solved as 
soon as possible, but at least they support simple tests. I used a very 
simple configuration and I compared it to a replicated volume with the 
same level of fault tolerance.

The test environment has been 4 servers based on an Intel Atom D525 1.8 
GHz dual core with 4GB of RAM and 1 TB disk. They are interconnected 
through a dedicated 1Gbit switch (this is the environment that I can 
dispose of regularly for my tests). 3 servers have been used as bricks, 
and the fourth one has been the client.

The dispersed volume is composed of 3 bricks, with one of them of 
redundancy. This has been compared to an standard replica-2 volume with 
2 bricks.

The tests consist on the sequential write of 1GB file using different 
block sizes (all writes aligned to the ida block size). All tests have 
been executed 10 times and the average has been taken. IOPS represents 
the average number of user-side write operations of the current block 
size that can done per second.

The results are attached in an ods document. This is very preliminary, 
it can change, use it with caution.

As you will see, the network becomes a bottleneck for both tests when 
the block size if big enough.

As an additional comparison, an example scenario with 6 bricks of 1 TB 
would have 3 TB of logical space in a distributed-replicated volume, but 
4 TB in a distributed-dispersed volume, a 33% more space but with the 
same level of fault tolerance.

Xavi
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