Managed Service for Greenplum® clusters and hosts

• What is a database host and database cluster?

• How many database hosts can there be in one cluster?

• How many clusters can you create in a single cloud?

• How are DB clusters maintained?

• How do you calculate usage cost for a database host?

• Why is the cluster slow even though the computing resources are not used fully?

• Why do I get an error about minimum memory for Greenplum® processes?

What is a database host and database cluster?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 you can configure replication.

How many database hosts can there be in one cluster?How many database hosts can there be in one cluster?

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?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?How are DB clusters maintained?

In Managed Service for Greenplum®, maintenance 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?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 for each host class in the Pricing policy section.

Why is the cluster slow even though the computing resources are not used fully?Why is the cluster slow even though the computing resources are not used fully?

Your storage may have insufficient maximum IOPS and bandwidth to process the current number of requests. In this case, throttling occurs, which degrades the entire cluster performance.

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:

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.

Why do I get the minimum memory error for Greenplum® processes?Why do I get the minimum memory error for Greenplum® processes?

When creating, modifying, or restoring a cluster, you may get this error:

Per process memory must be more then '20971520' bytes on segment host, got '<calculated_memory_size>'

This error occurs if the memory size for each Greenplum® process is less than 20 MB and the number of connections equals the max_connections value. Minimum memory per cluster process is calculated using the following formula:

<host_segment_RAM> ÷ (<max_connections> x <number_of_segments_per_host>)

To fix the error, do one of the following:

• Reduce the max_connections value.
• Increase memory size by changing the segment host class.

Greenplum® and Greenplum Database® are registered trademarks or trademarks of VMware, Inc. in the United States and/or other countries.