Managed Service for Greenplum® clusters and hosts
What is a database host and database cluster?
A database host is an isolated database environment in the cloud infrastructure with dedicated computing resources and reserved data storage.
A database cluster is one or more database hosts between which replication can be configured.
How many DB hosts can a cluster contain?
A Managed Service for Greenplum® cluster includes a minimum of 4 hosts:
- 2 master hosts.
- 2 segment hosts.
You can increase the number of segment hosts up to 32.
For more information, see Quotas and limits.
How many clusters can you create in a single cloud?
For more information on MDB technical and organizational limitations, see Quotas and limits.
How are DB clusters maintained?
Maintenance in Managed Service for Greenplum® implies:
- Automatic installation of DBMS updates and fixes for your database hosts.
- Changes to the host class and storage size.
- Other Managed Service for Greenplum® maintenance activities.
For more information, see Maintenance.
How do you calculate usage cost for a database host?
In Managed Service for Greenplum®, the usage cost is calculated based on the following parameters:
- Selected host class.
- Size of the storage reserved for the database host.
- Size of the database cluster backups. Backup space in the amount of the reserved storage is free of charge. Backup storage that exceeds this size is charged at special rates.
- Number of hours of database host operation. Partial hours are rounded to an integer value. You can find the cost per hour of operation for each host class in Pricing policy.
Why is the cluster slow even though the computing resources are not used fully?
Perhaps, the maximum storage IOPS and bandwidth values are insufficient for processing the current number of requests. In this case, throttling is triggered and the performance of the entire cluster degrades.
The maximum IOPS and bandwidth values increase by a fixed value when the storage size increases by a certain step. The step and increment values depend on the disk type:
| Disk type | Step, GB | Max IOPS increase (read/write) | Max bandwidth increase (read/write), MB/s |
|---|---|---|---|
network-hdd |
256 | 300/300 | 30/30 |
network-ssd |
32 | 1,000/1,000 | 15/15 |
network-ssd-nonreplicated |
93 | 28,000/5,600 | 110/82 |
To increase the maximum IOPS and bandwidth values and make throttling less likely, increase the storage size when you update your cluster.
If you are using the network-hdd storage type, consider switching to network-ssd or network-ssd-nonreplicated by restoring the cluster from a backup.
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