HDFS articles

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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. Continue Reading →

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. Continue Reading →

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. Continue Reading →

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. Continue Reading →

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. Continue Reading →

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. Continue Reading →

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. Continue Reading →

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. Continue Reading →