Databases & Analytics - Handling «Disk Full» situations – Support Guides

Learn about how Cloud Databases and Analytics services behave before and when reaching such conditions, and what you can do about it.

No matter the engine technology, when no more physical disk space is available, the service operation degrades significantly. At the very least, your services cannot store any more data, but even logical read operations might start to get impacted, for example, querying might slow down or fail.

Requirements

Access to the OVHcloud Control Panel
A Cloud Database and Analytics service up and running

Instructions

Avoiding full disk conditions

Disk space usage metrics

To use your Cloud Databases and Analytics service efficiently, you should monitor service metrics. You can access those in the OVHcloud Control Panel or using the API. You can also make use of cross-service integrations to gather, observe, and alert based on service metrics.

Mail notifications

When your service storage begins to fill up and reaches a high mark, your service sends you an email to warn you of the situation. The specific threshold depends on the engine; it may range from 75 to 90 percent.

When the disk usage increases even more and reaches a critical level (depending on the engine, ranging from 90 to 95 percent), you will receive another email notification, and the service will turn to a "disk full" mode, where it will start to refuse writes.

How to handle a disk full situation?

Different engines react in different ways, thus your services react differently when facing disk full conditions*:

Valkey, Kafka® MirrorMaker, Dashboard, and Kafka® Connect do not store any user data on disk. Thus, they will not fill up the underlying disk storage.
Kafka® and OpenSearch™ turn to read-only.
MySQL® and PostgreSQL® turn to read-only with a way to temporarily revert to read-write.
MongoDB® forbids writes but allows deletes for Admin users.

Upgrading your service

It may be that your usage simply requires more storage. You can then increase the provisioned storage and/or upgrade to an offer with more storage. Once the upgrade finishes, the service will detect that more storage is available and thus revert to normal mode.

Reclaim disk space

It may be that you have reached the full disk situation because of a runaway application filling up your service, or that you are storing some old, obsolete data. In these cases, stop whatever process is unduly filling up your storage, then remove unwanted data.

Kafka®, OpenSearch™

You can reclaim disk space by deleting a Kafka® topic or an OpenSearch™ index.

MongoDB®

MongoDB® blocks all write operations when the disk is full, except for the Admin users who can execute any MongoDB® command to reclaim disk space.

PostgreSQL®, MySQL®

For these engines, call the respective API endpoint to temporarily allow write operations:

PostgreSQL®:

POST /cloud/project/{serviceName}/database/postgresql/{clusterId}/enableWrites
MySQL®:

POST /cloud/project/{serviceName}/database/mysql/{clusterId}/enableWrites

This will give you a 15-minute time window to write to your database. At the end of this window, either you were able to execute queries that reduce disk usage (e.g., DROPs, DELETEs), allowing your service changes to the read-write state, or disk usage stays too high and your service will return to the read-only state.

NOTE: Be careful not to use that write window to continue to increase disk usage; this might fill the underlying storage space. PostgreSQL® and MySQL® will not react well to such a situation and might end up irrevocably out of order.

Go further

For more information and tutorials, please see our other Managed Databases & Analytics or Platform as a Service guides. You can also explore the guides for other OVHcloud products and services.

OVHcloud Managed Databases and Analytics:

Grafana® is a registered trademark of Grafana Labs and is used with the permission of Grafana Labs. OVH SAS and its subsidiaries are not affiliated with or endorsed by Grafana Labs.
Kafka® is a registered trademark of The Apache Software Foundation and has been licensed for use by OVHcloud, who has no affiliation with and is not endorsed by The Apache Software Foundation.
MongoDB® is a registered trademark of MongoDB, Inc.
MySQL® is a registered trademark of Oracle and/or its affiliates.
PostgreSQL® is a registered trademark of the PostgreSQL Community Association of Canada.