Question:- What version of Hadoop do I need to run HBase?
Answer:- Different versions of HBase require different versions of Hadoop. Consult the table below to find which version of Hadoop you will need: HBase Release Number Hadoop Release Number 0.1.x 0.16.x 0.2.x 0.17.x 0.18.x 0.18.x 0.19.x 0.19.x 0.20.x 0.20.x 0.90.4 (current stable) ??? Releases of Hadoop can be found here. We recommend using the most recent version of Hadoop possible, as it will contain the most bug fixes. Note that HBase-0.2.x can be made to work on Hadoop-0.18.x. HBase-0.2.x ships with Hadoop-0.17.x, so to use Hadoop-0.18.x you must recompile Hadoop-0.18.x, remove the Hadoop-0.17.x jars from HBase, and replace them with the jars from Hadoop-0.18.x. Also note that after HBase-0.2.x, the HBase release numbering schema will change to align with the Hadoop release number on which it depends.
Question:- Compare MongoDB with Cassandra.
Answer:- • MongoDB • Document • Read • Multi-indexed • Cassandra • Google Bigtable like • Write • Using Key or Scan
Question:- What is Cassandra?
Answer:- Cassandra is one of the most favored NoSQL distributed database management systems by Apache. With its open-source technology, Cassandra is efficiently designed to store and manage large volumes of data without any failure. Highly scalable for Big Data models and originally designed by Facebook, Apache Cassandra is written in Java comprising flexible schemas. Apache Cassandra has no single point of failure. There are various types of NoSQL databases, and Cassandra is a hybrid of column-oriented and key–value store database. The keyspace is the outermost container for an application, and the table or column family in Cassandra is the keyspace entity.
Question:- List the benefits of using Cassandra.
Answer:- Unlike traditional or any other database, Apache Cassandra delivers near real-time performance simplifying the work of Developers, Administrators, Data Analysts, and Software Engineers. • Instead of master–slave architecture, Cassandra is established on a peer-to-peer architecture ensuring no failure. • It also assures phenomenal flexibility as it allows the insertion of multiple nodes to any Cassandra cluster in any data center. Further, any client can forward its request to any server. • Cassandra facilitates extensible scalability and can be easily scaled up and scaled down as per the requirements. With a high throughput for read and write operations, this NoSQL application need not be restarted while scaling. • Cassandra is also revered for its strong data replication on nodes capability as it allows data storage at multiple locations enabling users to retrieve data from another location if one node fails. Users have the option to set up the number of replicas they want to create. • Shows brilliant performance when used for massive datasets and thus, the most preferable NoSQL DB by most organizations. • Operates on column-oriented structure and thus, quickens and simplifies the process of slicing. Even data access and retrieval becomes more efficient with column-based data model. • Further, Apache Cassandra supports schema-free/schema-optional data model, which un-necessitate the purpose of showing all the columns required by your application.Find out how Cassandra Versus MongoDB can help you get ahead in your career!
Question:- Explain the concept of tunable consistency in Cassandra.
Answer:- Tunable consistency is a phenomenal character that makes Cassandra a favored database choice of Developers, Analysts, and Big data Architects. Consistency refers to the up-to-date and synchronized data rows on all their replicas. Cassandra’s tunable consistency allows users to select the consistency level best suited for their use cases. It supports two consistencies: eventual consistency and strong consistency. The former guarantees consistency when no new updates are made on a given data item, i.e., all accesses return the last updated value eventually. Systems with eventual consistency are known to have achieved replica convergence. For strong consistency, Cassandra supports the following condition: R + W > N where, N – Number of replicas W – Number of nodes that need to agree for a successful write R – Number of nodes that need to agree for a successful read
Question:- How does Cassandra write?
Answer:- Cassandra performs the write function by applying two commits: first, it writes to a commit log on the disk, and then it commits to an in-memory structure known as memtable. Once the two commits are successful, the write is achieved. Writes are written in the table structure as SSTables (sorted string tables). Cassandra offers faster write performance.
Question:- Define the management tools in Cassandra.
Answer:- DataStax OpsCenter: It is the Internet-based management and monitoring solution for Cassandra cluster and DataStax. It is free to download and includes an additional edition of OpsCenter. SPM primarily administers Cassandra metrics and various OS and JVM metrics. Besides Cassandra, SPM also monitors Hadoop, Spark, Solr, Storm, ZooKeeper, and other Big Data platforms. The main features of SPM include correlation of events and metrics, distributed transaction tracing, creating real-time graphs with zooming, anomaly detection, and heartbeat alerting.
Question:- Define memtable.
Answer:- Similar to a table, a memtable is the in-memory/write-back cache space consisting of the content in a key and column format. The data in a memtable is sorted by key, and each column family consists of a distinct memtable that retrieves column data via the key. It stores the writes until it is full, and then flushes them out.
Question:- What is SSTable? How is it different from other relational tables?
Answer:- SSTable expands to ‘Sorted String Table,’ which refers to an important data file in Cassandra and accepts regular written memtables. They are stored on disk and exist for each Cassandra table. Exhibiting immutability, SSTables do not allow any further addition and removal of data items once written. For each SSTable, Cassandra creates three separate files like partition index, partition summary, and a bloom filter.
Question:- Explain the concept of Bloom Filter.
Answer:- Associated with SSTable, Bloom filter is an off-heap (off the Java heap to native memory) data structure to check whether there is any data available in the SSTable before performing any I/O disk operation.
Question:- Explain CAP Theorem.
Answer:- With a strong requirement to scale systems when additional resources are needed, CAP Theorem plays a major role in maintaining the scaling strategy. It is an efficient way to handle scaling in distributed systems. Consistency, availability, and partition tolerance (CAP) theorem states that in distributed systems like Cassandra, users can enjoy only two out of these three characteristics. One of them needs to be sacrificed. Consistency guarantees the return of most recent write for the client; availability returns a rational response within minimum time; and in partition tolerance, the system will continue its operations when network partitions occur. The two options available are AP and CP.
Question:- State the differences between a node, a cluster, and a data center in Cassandra.
Answer:- There are various components of Cassandra. While a node is a single machine running Cassandra, cluster is a collection of nodes that have similar types of data grouped together. Data centers are useful components when serving customers in different geographical areas. You can group different nodes of a cluster into different data centers.
Question:- How to write a query in Cassandra?
Answer:- Using CQL (Cassandra Query Language) we can write queries in Cassandra. Cqlsh is used for interacting with the database.
Question:- What OS does Cassandra support?
Answer:- Cassandra supports both Windows and Linux.