How Is the Disk Space or Capacity of GaussDB(DWS) Calculated?
- If a GaussDB(DWS) storage-compute coupled cluster has three data nodes and each node is 320 GB, the total capacity is 960 GB. When 1 GB data is stored, GaussDB(DWS) stores 1 GB data on two nodes due to duplication, a security mechanism, thereby occupying a total of 2 GB space. As a result, more than 2 GB space is occupied if metadata and indexes are calculated. Therefore, a three-node cluster with a total capacity of 960 GB can store 480 GB data. This mechanism ensures data security. In the storage-compute decoupling scenario, disks are used as cache disks with capacities that match their actual sizes. There are three data nodes with decoupled storage and compute, each having a capacity of 320 GB, resulting in a total capacity of 960 GB.
When you create a cluster on the GaussDB(DWS) console, the capacity of a node is displayed on the page. For example, the disk size of the storage-compute coupled dwsx2.xlarge node is 160 GB on the creation page. However, the actual disk size of the node is 320 GB, which is displayed as 160 GB. In this way, you can create a node based on the actual disk data. For instance, on the creation page, the dwsx3.4U16G.4DPU flavor of a storage-compute decoupled cluster has a specified capacity of 320 GB, and the applied disk capacity is also 320 GB. The capacity displayed on the page is the actual applied capacity.
- Check the disk usage of a single node.
Similarly, if the total capacity is 960 GB and there are three data nodes, the disk capacity of each node is 320 GB.
Log in to the GaussDB(DWS) console and choose Monitoring > Node Monitoring > Overview to view the usage of disks and other resources on each node.
- The disk space shown on the node management page represents the combined capacity of all disks in the GaussDB(DWS) cluster, including system disks and data disks. On the overview page of a storage-compute coupled cluster, the displayed disk space only refers to the available space for storing table data in the cluster. Additionally, the GaussDB(DWS) cluster has backup copies of tables, which also occupy disk storage. The disk space shown on the overview page of a storage-compute coupled cluster represents the cache size, which corresponds to the actual disk space utilized.
- If the cluster is read-only and an alarm for insufficient disk space is generated, scale out the cluster by following the instructions provided in Scaling Out a Cluster.
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