50 lines
2.8 KiB
ReStructuredText
50 lines
2.8 KiB
ReStructuredText
:original_name: en-us_topic_0054235826.html
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.. _en-us_topic_0054235826:
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DCS
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===
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Distributed Cache Service (DCS) is an online, distributed, in-memory cache service compatible with Redis. It is reliable, scalable, usable out of the box, and easy to manage, meeting your requirements for high read/write performance and fast data access.
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Clients can access DCS instances only when they are installed on (ECSs) and belong to the same virtual private cloud (VPC) as the DCS instances.
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.. figure:: /_static/images/en-us_image_0000001287445428.png
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:alt: **Figure 1** Accessing DCS instances
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**Figure 1** Accessing DCS instances
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.. note::
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Like clients, DCS instances are also run on ECSs. A client must belong to the same VPC and subnet as the DCS instance it is attempting to access.
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DCS Redis
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---------
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DCS uses Redis 3.0, a storage system that supports multiple types of datastructures, including key-value pairs. It can be used in scenarios such as caching, event pub/sub, and high-speed queuing. Redis is networked and written in ANSI C. It supports direct read/write of strings, hashes, lists, queues, and sets. Redis workswith in-memory datasets and provides persistence. For more information about Redis, visit https://redis.io/.
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There are three deployment modes for DCS Redis instances:
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- Single-node
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Each DCS instance runs on only one cache node. Such DCS instances are mainly used for temporary data storage but are not suitable for high-reliability service scenarios.
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Single-node DCS instances support intensive concurrent read/write operations, but do not implement data persistence. Data will be deleted after single-node DCS instances are restarted.
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- Master/Standby
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DCS instances run in master/standby mode, providing higher availability than single-node DCS instances.
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- Each DCS instance runs on two cache nodes (one master and one standby), and supports data persistence.
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- The standby node is invisible to the client and does not provide data read/write services. It is kept synchronized with the master node through data synchronization.
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- The standby node takes over automatically if the master node fails.
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- Proxy Cluster
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DCS instances run in Proxy Cluster mode, providing higher instance specifications and performance than master/standby DCS instances:
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- Each DCS instance has at least three master nodes. Compared with master/standby DCS instances, DCS instances in Proxy Cluster mode support higher instance specifications and concurrency.
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- Each master node has a redundant node. If a master node is faulty, the redundant node becomes the master node and provides data read/write services for users.
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- Each redundant node is invisible to Redis clients, and it is kept synchronized with its master node through data synchronization.
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