Introduction to Data Lakes

Data
Lakes are the new hot topic in the big data and BI communities. Data Lakes have
been around for a few years now, but have only gained popular notice within the
last year. In this blog I will take you through the concept of a Data
Lake, so that you can begin your own voyage on the lakes.

What
is a Data Lake?

Before
we can answer this question, it’s worth reflecting on a concept which most of
us know and love – Data Warehouses. A Data Warehouse is a form of
data architecture. The core principal of a Data Warehouse isn’t the
database, it’s the data architecture which the database and tools implement.
Conceptually, the condensed and isolated features of a Data Warehouse are
around:

1.
Data acquisition

2.
Data management

3.
Data delivery /
access

A Data Lake is similar to a Data Warehouse in these
regards. It is an architecture. The technology which underpins a Data Lake
enables the architecture of the lake to flow and develop. Conceptually, the
architecture of a Data Lake wants to acquire data, it needs careful, yet agile
management, and the results of any exploration of the data should be made
accessible. The two architectures can be used together, but conceptually the
similarities end here.

Conceptually, Data Lakes and Data Warehouses are
broadly similar yet the approaches are vastly different. So let’s leave Data
Warehousing here and dive deeper into Data Lakes.

Fundamentally, a Data Lake is just not a
repository. It is a series of containers which capture, manage and explore
any form of raw data at scale, enabled by low cost technologies, from which
multiple downstream applications can access valuable insight which was previously inaccessible.

How Do Data Lakes Work?

Conceptually, a Data Lake is similar to a real lake
– water flows in, fills up the reservoir and flows out again. The incoming flow
represents multiple raw data formats, ranging from emails, sensor data,
spreadsheets, relational data, social media content, etc. The reservoir
represents the store of the raw data, where analytics can be run on all or some
of the data. The outflow is the analysed data, which is made accessible to
users.

To break it down, most Data Lake architectures come
as two parts. Firstly, there is a large distributed storage engine with very
few rules/limitations. This provides a repository for data of any size and
shape. It can hold a mixture of relational data structures, semi-structured
flat files and completely unstructured data dumps. The fundamental point is
that it can store any type of data you may need to analyse. The data is spread
across a distributed array of cheap storage that can be accessed independently.

There is then a scalable compute layer, designed to
take a traditional SQL-style query and break it into small parts that can then
be run massively in parallel because of the distributed nature of the disks.

In essence – we are overcoming the limitations of
traditional querying by:

·       Separating
compute so it can scale independently

·       Parallelizing
storage to reduce impact of I/O bottlenecks

There
are various technologies and design patterns which form the basis of Data
Lakes. In terms of technologies these include:

·
Azure Data Lake

·
Cassandra

·
Hadoop

·
S3

·
Teradata

With regards to design patterns, these will be
explored in due course. However, before we get there, there are some challenges
which you must be made aware of. These challenges are:

1.
Data dumping –
It’s very easy to treat a data lake as a dumping ground for anything and
everything. This will essentially create a data swamp, which no one will want
to go into.

2.
Data drowning –
the volume of the data could be massive and the velocity very fast. There is a
real risk of drowning by not fully knowing what data you have in your lake.

These challenges require good design and
governance, which will be covered off in the near future.

Hopefully this has given you a brief, yet
comprehensive high-level overview of what data lakes are. We will be focusing
on Azure Data Lake, which is a management implementation of the Hadoop
architectures. Further reading on Azure Data Lake can be found below.

Further Reading

In order to know more about Data Lakes the
following resources are invaluable.

Getting
Started With Azure Data Lake Store

Getting
Started With Azure Data Lake Analytics and U-SQL

Azure Data
Lake Overview