Understanding the value of Data Lake(s) I

Tech loves buzzwords. Data lake is a big thing with Big Data. Before we go crazy technical, try to simplify the term. What comes to mind when you think of a data lake? First, it’s two words: data and lake.

Data: You remember this one from primary school. Unprocessed or raw information, facts and figures, all in their various formats. .MP3, .DOC, .CSV, .JPG etc.

Lake: A large body of water, simply put. I think of my weekend camping trip in Lake George, but in this context, a lake will be a storage for data, and not water.

Now think of yourself. What do you need data for? To get work done. For example, I need to write a research paper. I generate some original ideas, and source for some more. I need to document and compile my findings. I research, type up, save what I want, and store of the content in some kind of database, to use the term loosely, for future use or reference. For now I’ll just save in folders on my laptop or my Google Drive (Box sometimes, my Dropbox is full). Whenever I need it, all I need to do is search (query) and retrieve.

Right! Data, lake, base but I’m really thinking about a hard drive. When do I need one or the other?

Nuances. A database is really a collection or repository of information that’s organized so that it can easily be accessed, managed and updated. [1] My hard drive is a storage medium. It is my local data repository, my local database on my laptop.

Now picture several people having similar needs as you, not limited to students across the globe writing research papers, or people working in an organization, all constantly needing data to get all sorts of work done, you’ll start to see why a hard drive is no longer enough. Now a client-server model is important. Entire computers need to be dedicated now, to provide database services using computer programs to other computer programs, using a client-server model. That is what a database server does.

My hard drive or disk is clearly not a server. However servers are made up of hard disks. Local storage media include disk, tape – the magnetic ones such as floppy and cassettes, or memory. Data is stored onto the hard disk in form of files, a collection of bytes.

Having cleared these nuances, or at least attempted to, let’s crank it up a notch and think enterprise. By that, I mean scale, which is where a Database Management System (DBMS) comes in. Of course, the database and the DBMS are two separate things. The DBMS is a system software. It creates and manages the database, and interfaces between the database and the end user(s) or an app. Fundamentally, it manages the data, the database engine, and the database schema, and users can Create, Read, Update, Delete (CRUD) data in a database.

In the enterprise, more users are doing CRUD frequently and need a single version of the truth. In that case, the data (base) needs to be ACID (atomic, consistent, isolated, durable). So you see how the news of the Swift hack was a big deal.

That helps. Now that I know better, I can ask better questions, like what is the difference between a database and a data lake?

I think this is enough for one post. Now we got the introduction, let’s look at that in a sequel. (How does Wikipedia do it?)



  1. Database, TechTarget.com http://searchsqlserver.techtarget.com/definition/database

Rethinking commodity hardware for Hadoop

Traditionally, the idea of deploying Hadoop on commodity hardware was genius. With this option of low cost infrastructure, Hadoop was in fact was designed to be the RAID of compute farms – made up of homogeneous, generally cheap and easily replaceable servers. This model does work, but when big data starts to really scale, and I mean really scale, the terms ‘commodity’ and ‘cheap’ start to go from hand-in-hand to tongue-in-cheek. In order words, it would be an oversight and in poor taste to make long term goals for these two.

Get to your point already?

Infrastructure solutions come as servers with internal storage. Stripped down to the basics, they perform two functions: compute and storage. The issue with this is the reason behind the term ‘Big Data.’ The data will grow. As this growth occurs (the technical term is scale), more and more storage would be needed to house the data. You could store this data on servers of course, but if your need is really to store, then you probably don’t need the compute resources. And that’s where the challenge begins. Because traditional commodity servers have their storage and compute resources are joined at the hip, this is a quick way to under-utilize the resources, which is not cost effective.

So hey, why don’t you use external storage?

Well, great question. That’s definitely an option but there’s a  whole “movement” about moving the analytics to the data, which we could pick apart. Keeping the storage local means faster jobs. The moment you move the data across a network to external storage, you are susceptible to issues that accompany network and storage bandwidth – the good, the bad and it could get real ugly (e.g. complexity, latency, loss of features, loss of data governance, more infrastructure). So ideally, you want your data to be local – on local disks, which is also where your programs run.

Having said that, at the enterprise level, data resides on SANs – Storage Area Networks, and must be moved to compute nodes for processing. To optimize infrastructure and reduce data bottlenecks, the nodes should be on the same cluster.

So what else is there to Hadoop and commodity hardware?

High availability is essential to Hadoop, which is simply a mechanism to avoid having a single point of failure (SPOF) in the overall system. Thus to incorporate redundancy, the recommendation is to have more than one copy, and with Hadoop, specifically three copies of the data. And just as you see through the good intentions, you also see the implications of scale. This single move of replicating the data in three would result in replicating local disks, as well as scaling server and disk together. Again, the demon of under-utilization rears its head, causing the physical footprint of the datacenter to multiply. What a mess!

One popular use of Hadoop is as a data warehouse. If you’re considering doing this, i.e modernizing your existing/traditional data warehose solution, also be mindful of the impact of scaling on your datacenter and the associated costs which are not limited to:

  • Personnel: administrators for deployment and day to day operations
  • Network: bottlenecks, bandwidth and (re)solutions
  • Workloads: nature of jobs, needs – data streaming, or at data at rest
  • Software licensing (operating systems, applications) per node/cluster