Over the past few years, data science has been one of the most sought-after multidisciplinary fields in the world today. It has established itself as an essential component of numerous industries such as marketing optimisation, risk management, marketing analytics. fraud detection, agriculture, etc. Understandably, this has lead to increasing demand for resorting to different approaches to data.
When we talk about Apache Spark and Hadoop, it is really difficult to compare them with each other. We should be aware that both possess important features in the world of data science and big data. Hadoop excels over Apache Spark in some business applications, but when processing speed and ease of use is taken into account, Apache Spark has its own advantages that make it unique. The most important thing to note is, neither of these two can replace each other. However, since they are compatible with each other, they can be used together to produce very effective results for many big data applications.
To analyse how important these two platforms are, there is a set of parameters with which we can discuss their efficiencies such as performance, ease of use, cost, data processing, compatibility, fault tolerance, scalability, and security. In this article, we will talk about Apache Spark and Hadoop individually for a bit, followed by stressing these parameters to better understand their significance in data science and big data.
Hadoop, also known as Apache Hadoop, is a project formed by Apache.org that includes a software library and a framework that enables the usage of simple programming models to distributed processing of large data sets (big data) across computer clusters. Hadoop is quite efficient in scaling up from single computer systems to a lot of commodity system, offering substantial local storage. Due to this, Hadoop is considered as an omnipresent heavyweight in the big data analytics space.
There are modules that work together to form the Hadoop framework. Here are the main Hadoop framework modules:
Hadoop’s core is based on the above four modules followed by many others like Ambari, Avro, Cassandra, Hive, Pig, Oozie, Flume, and Sqoop. These are responsible for improving and extending Hadoop’s power to big data applications and large data set processing.
Hadoop is utilised by numerous companies using big data sets and analytics and is the de facto model for big data applications. Initially, it was designed to take care of crawling and searching billions of web pages and collecting their information into a database, This resulted in Hadoop Distributed File System (HDFS), a distributed file system designed to run on commodity hardware and Hadoop MapReduce, a processing technique and a program model for distributed computing based on java.
Hadoop comes handy when companies find data sets too large and complex to not being able to process the information in reasonably sufficient time. Since crawling and searching the web are text-based tasks, Hadoop MapReduce comes in handy as it is an exceptional text processing engine.
An open-source distributed general-purpose cluster-computing framework, Apache Spark is considered as a fast and general engine for large-scale data processing. Compared to heavyweight Hadoop’s Big Data framework, Spark is very lightweight and faster by nearly 100 times. Although the facts say so, in fact, Spark runs up to 10 times faster on disk. Apart from that, it can perform batch processing but it really is good at streaming workloads, interactive queries, and machine-based learning.
Spark engine’s real-time data processing capability has a clear edge over Hadoop MapReduce’s disk-bound, batch processing one. Not only is Spark compatible with Hadoop and its modules, but it is also listed as a module on Hadoop’s project page. And because Spark can run in Hadoop clusters through YARN (Yet Another Resource Negotiator), it has its own page and a standalone mode. It can run as a Hadoop module and as a standalone solution which makes it difficult to make direct comparisons.
Despite these facts, Spark is expected to diverge and might even replace Hadoop, especially in terms of faster access to processed data. Spark’s cluster computing feature enables it to compete with only Hadoop MapReduce and not the entire Hadoop ecosystem. That is why it can use HDFS despite not having its own distributed file system. To be concise, Hadoop MapReduce uses persistent storage whereas Spark uses Resilient Distributed Datasets (RDDs). What is RDD? This will be stressed in the Fault Tolerance section.
Let us have a look at the parameters using which we can compare the features of Apache Spark with Hadoop.
|Processes everything in memory||Performance-wise||Hadoop MapReduce uses batch processing|
|Has user-friendly APIs for multiple programming languages||Ease of Use||Has add-ons such as Hive and Pig|
|Spark systems cost more||Costs||Hadoop MapReduce systems cost lesser|
|Shares every Hadoop MapReduce compatibility||Compatibility||Compliments Apache Spark seamlessly|
|Has GraphX, its own graph computation library||Data Processing||Hadoop MapReduce operates in sequential steps|
|Spark uses Resilient Distributed Datasets (RDDs)||Fault Tolerance||Utilises TaskTrackers to keep the JobTracker ticking|
|Comparatively lesser scalability||Scalability||Large Scalability|
|Provides authentication via shared secret (password authentication)||Security||Supports Kerberos authentication|
Spark is definitely faster when compared to Hadoop MapReduce. However, they cannot be compared because they perform processing in different styles. Spark is way faster because it processes everything in memory, even using disk for data that does not all fit into memory.
The in-memory processing of Spark performs near real-time analytics for data from machine learning, log monitoring, marketing campaigns, Internet of Things sensors, security analytics, and social media sites. Hadoop MapReduce, on the other hand, utilises the batch-processing method so it understandably was never created for mesmerising speed. As a matter of fact, it was initially created to continuously gather information from websites during the times when data in or near real-time were not required.
Spark does not only have a good reputation for its excellent performance, but it is also relatively easy to use along with providing additional support for languages like user-friendly APIs for Scala, Java, Python, and Spark SQL. Since Spark SQL is quite comparable to SQL 92, the user requires no additional knowledge to use it.
Additionally, Spark is armed with an interactive mode to allow developers and users get instant feedback for questions and other actions. Hadoop MapReduce makes up for the lack of any interactive mode with add-ons like Hive and Pig, thus easing the workflow of Hadoop MapReduce.
Apache Spark and Apache Hadoop MapReduce are both free open-source software.
However, because Hadoop MapReduce’s processing is disk-based, it utilises standard volumes of memory. This results in companies buying faster disks with a lot of disk space to run Hadoop MapReduce. In stark contrast to this, Spark requires a lot of memory but compensates by settling with a standard amount of disk space running at standard speeds.
Both Spark and Hadoop MapReduce are compatible with each other. Moreover, Spark shares every Hadoop MapReduce compatibility for data sources, file formats, and business intelligence tools via JDBC and ODBC.
Hadoop MapReduce is a batch-processing engine. So how does it work? Well, it works in sequential steps.
Step 1: Reads data from the cluster
Step 2: Performs its operation on the data
Step 3: Writes the results back to the cluster
Step 4: Reads updated data from the cluster
Step 5: Performs the next data operation
Step 6: Writes those results back to the cluster
Step 7: Repeat.
Spark performs in a similar manner, but the process doesn’t go on. It includes a single step and then to memory.
Step 1: Reads data from the cluster
Step 2: Performs its operation on the data
Step 3: Writes it back to the cluster.
Moreover, Spark has GraphX, its own graph computation library. GraphX presents the same data as graphs and collections. Users have the option to use Resilient Distributed Datasets (RDDs) to transform and join graphs. This will be further addressed below in the Fault Tolerance section.
There are two different ways in which Hadoop MapReduce and Spark resolve the fault tolerance issue. Hadoop MapReduce utilises nodes like TaskTrackers to keep the JobTracker ticking. On the process being interrupted, the JobTracker reassigns every pending and in-progress operation to another TaskTracker. Although this process effectively provides fault tolerance, the completion times might get majorly affected even for operations having just a single failure.
Spark, in this case, applies Resilient Distributed Datasets (RDDs), fault-tolerant collections of elements that can be operated side by side. References can be provided by RDDs in the form of datasets in an external storage system like shared filesystems, HDFS, HBase, or whatever available data source. This results in allowing a Hadoop InputFormat and Spark can create RDDs from every storage source that is backed by Hadoop. That covers local filesystems or one of those listed earlier.
The persistence of RDDs to cache a dataset in memory across operations enables the speeding up of future actions by possibly ten folds. The cache of Spark is fault-tolerant, it will recomputed automatically by making use of the original transformations provided any partition of an RDD is lost.
In terms of scaling up, both Hadoop MapReduce and Spark are on equal terms in using the HDFS. Reports say that Yahoo holds a 42,000 node Hadoop cluster with no bounds while the most comprehensive Spark cluster holds 8,000 nodes. However, in order to support output expectations, the cluster sizes are expected to grow along with that of big data.
Kerberos authentication, considered to be quite hectic to manage is supported by Hadoop. Nevertheless, companies have been assisted by third-party vendors to leverage Active Directory Kerberos and LDAP for authentication and also allow data encrypt for in-flight and data at rest. Access control lists (ACLs) a traditional file permissions model are supported by Hadoop while it provides Service Level Authorization for user control in job submission, resulting in clients having the right permissions without any fail.
For Spark though, it presently offers somewhat inadequate security as it provides authentication via shared secret (password authentication). However, if the user runs Spark on HDFS, then it can utilise HDFS ACLs and file-level permissions. Moreover, running Spark on YARN will enable the latter to have the capacity of using Kerberos authentication. That is the security takeaway from using Spark.
Apache Spark and Apache Hadoop form the perfect combination for business applications. Where Hadoop MapReduce has been a revelation in the big data market for businesses requiring huge datasets to be brought under control by commodity systems, Apache Spark’s speed and comparative ease of use compliments the low-cost operation involving Hadoop MapReduce.
Like we discussed at the beginning of this article that neither of these two can replace one another, Spark and Hadoop form a lethal and effective symbiotic partnership. While Hadoop has features like a distributed file system that Spark does not have, the latter presents real-time, in-memory processing for the required data sets. Both Hadoop and Spark form the perfect combination for the ideal big data scenario. Rest assured, in this situation, both working in the same team is what goes in favour of big data professionals.
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