Storage articles

Looking for something else? Check the categories of Storage:

Apache Avro Apache Cassandra Apache Parquet Apache ZooKeeper Elasticsearch HDFS MySQL PostgreSQL Time series

If not, below you can find all articles belonging to Storage.

Recovery in HDFS

Recovery process in HDFS helps to achieve fault tolerance. It concerns as well worker pipeline as blocks.

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HDFS on disk explained

Among all previous posts we could learn a lot about HDFS transaction logs, operations on closed files and so on. Thanks to that we can take a look now on data structure of NameNode and DataNode.

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Checkpoint in HDFS

HDSF is not an exception in the Big Data world and as other actors, it also uses checkpoints.

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Handling small files in HDFS

HDFS is not well suited tool to store a lot of small files. Even if that's true, some methods exist to handle small files better.

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Snapshot in HDFS

Implementing snapshots in distributed file systems is not a simple job. It must take into account different aspects, such as file deletion or content changes, and keep file system consistent among them.

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Cache in HDFS

Hadoop 2.3.0 brought an in-memory caching layer to HDFS. Even if this is quite old feature (released in 02/2014), it's always beneficial to know it.

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Append and truncate in HDFS

Making an immutable distributed file system is easier than building a mutable one. HDFS, even if initially was destined to not changing data, supports mutability through 2 operations: append and truncate.

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FSImage in HDFS

Edit log would be useless without its complementary structure called FSImage.

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Edit log in HDFS

HDFS stores everything that happens on transaction log files. They're used during checkpoint and file system recovery. So, they take quite important place in HDFS architecture.

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States in HDFS

Replica and blocks are HDFS entities having more than 1 state in their whole lifecycle. Being aware of these states helps a lot to understand what happens when a new file is written.

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Replication in HDFS

HDFS is a fault-tolerant and resilient distributed file system. It wouldn't be possible without, among others, blocks replication.

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File operations in HDFS

Previous article presented theoretical information about HDFS files. This post deepens this topic.

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Files in HDFS

Files in HDFS are different from files from local file system. They're fault-tolerant, can be stored in different abstractions and are based on quite big blocks comparing to blocks in local file system.

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Introduction to HDFS

HDFS is one of most popular distributed file systems in our days. It changes from other older distributed file systems thanks to its reliability.

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Mapper in Cassandra Java API

Before writing some code in Apache Cassandra, we'll try to explore very interesting dependency - cassandra-driver-mapping.

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Cache in Apache Cassandra

I/O operations are slower than memory lookups. It's the reason why memory cache helps to improve performances, in Cassandra too.

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Collections in Apache Cassandra

One of interesting data types used in Apache Cassandra are collections. In our model we can freely use maps, sets or lists.

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Tables in Apache Cassandra

Because tables in Apache Cassandra are very similar to the tables of relational databases, this article describing them won't focus on basic points. Instead, we'll explore more Cassandra specific subjects, such as configuration or different types.

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Compaction in Apache Cassandra

Disk compaction helps to save space. Since Cassandra is supposed to store a lot of data, it can't miss this useful process.

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Partitioners in Apache Cassandra

Since Cassandra is distributed storage system, it holds data in different nodes. But how it determines data should be stored by each node ? It's the role of partitioners.

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