HDFS storage types

HDFS supports the following storage types:

• ARCHIVE - Archival storage is for very dense storage and is useful for rarely accessed data. This storage type is typically cheaper per TB than normal hard disks.
• DISK - Hard disk drives are relatively inexpensive and provide sequential I/O performance. This is the default storage type.
• SSD - Solid state drives are useful for storing hot data and I/O-intensive applications.
• RAM_DISK - This special in-memory storage type is used to accelerate low-durability, single-replica writes.

When you add the DataNode Data Directory, you can specify which type of storage it uses, by prefixing the path with the storage type, in brackets. If you do not specify a storage type, it is assumed to be DISK.