.. Licensed under the Apache License, Version 2.0 (the "License"); you may not
.. use this file except in compliance with the License. You may obtain a copy of
.. the License at
..
..   http://www.apache.org/licenses/LICENSE-2.0
..
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.. the License.

Introduction
============


Apache Crail (Incubating) is a fast multi-tiered distributed storage system designed from ground up for high-performance network and storage hardware. The unique features of Crail include:

* Zero-copy network access from userspace
* Integration of multiple storage tiers such DRAM, flash and disaggregated shared storage
* Ultra-low latencies for both meta data and data operations. For instance: opening, reading and closing a small file residing in the distributed DRAM tier less than 10 microseconds, which is in the same ballpark as some of the fastest RDMA-based key/value stores
* High-performance sequential read/write operations: For instance: read operations on large files residing in the distributed DRAM tier are typically limited only by the performance of the network
* Very low CPU consumption: a single core sharing both application and file system client can drive sequential read/write operations at the speed of up to 100Gbps and more
* Asynchronous API leveraging the asynchronous nature of RDMA-based networking hardware
* Extensible plugin architecture: new storage tiers tailored to specific hardware can be added easily

Crail is implemented in Java offering a Java API which integrates directly with the Java off-heap memory. Crail is designed for performance critical temporary data within a scope of a rack or two.