Storage

The Palomar architecture requires a highly available, distributed storage system for operation.

This page lists the supported storage options for Dovecot Pro.

Important

"Storage Support" in the Dovecot Pro context refers to the storage systems that are defined in the Product Definition and covered under Dovecot Pro SLA.

If a storage system is not listed here, it is NOT SUPPORTED by Dovecot/OX. No SLA agreement can be provided unless one of the storage systems listed below are used.

Note: Not all storage systems have the same level of support. The different support levels are described in detail below.

Mailbox Format

Dovecot Pro's obox plugin is the ONLY mailbox format supported in Palomar.

Migration from *dbox on Dovecot Pro 2.3

Customers using dbox on Dovecot Pro 2.3 MUST migrate users to obox on 3.x.

There is no support for direct physical mailbox conversion of dbox to obox.

Storage Systems

Note

There are no licensing cost differences between Premium and Basic storage systems.

Premium Storage Support

Premium support indicates that these systems are actively tested and developed against by Dovecot/OX.

Each release is certified to work on at least one version/installation of the system (identified in Release Notes for that release). This means that release testing has been directly performed against at least one version of the storage system for a given Dovecot Pro release.

Storage options in this level are guaranteed to have compatibility with the following:

• Authentication (at least 1 solution)
• Specific API behavior (including necessary request parameters needed to interact with the system)

Additional features of these storages may also be supported (i.e. AWS IAM). These additional features are noted below.

Execution/Operation/Configuration of the storages is NOT directly supported by OX. However, these solutions are classified as Premium support options because:

• Similar installations SHOULD behave similarly - the storage experience has been commoditized by the vendor by design.
• Vendor support is available.
• Cooperative engineering efforts with the vendor has been done to maximize performance and stability.

Scality sproxyd (RING)

Vendor website: Scality

sproxyd is the only Pro-supported geo-redundant (multi-site) capable solution.

All sizing and setup for a Scality system is handled by Scality.

Release Notes will identify the specific version of RING that was tested against.

AWS S3

Vendor website: AWS

IMPORTANT

This support option is for the S3 service as provided by AWS on their platform. This is not generic S3 API support (see below).

AWS S3 is supported in a single region, although use of multiple availability-zones in that region with Palomar is acceptable.

The Dovecot Pro customer is responsible for working with AWS to ensure sufficient operational limits are configured for their storage bucket(s) (e.g., IOps and ingress/egress limits).

Dovecot Pro supports IAM (both v2 and v4 signatures).

Dovecot Pro uses (and tests) these specific S3 API commands.

Release Notes will identify:

• The month & year the S3 service was tested against
• The region where the testing occurred
• A link to the active documentation at the time testing occurred

Basic Storage Support

Basic support indicates that Dovecot Pro maintains access via a specified API interface that can be used to interact with the storage, but it does not certify actual storage vendors and does not test directly against these systems prior to any release version.

OX will not support any additional features other than basic API compatibility defined in the Product Definition.

OX cannot guarantee or troubleshoot storage performance or behavior.

Execution/Operation/Configuration of the storages is NOT directly supported by OX. Vendor support is storage dependent.

Customer assumes the risk if a storage vendor's API changes in the future.

OX/Dovecot Assistance

If something breaks in an existing production system, OX will use best efforts to work with the customer and fix the issue. However, this is not an SLA event and the customer should understand that quick and efficient fixes may be difficult as the Dovecot team does not have direct access to the storage systems locally to test/debug against (compare this to Premium storages, where the storage systems are locally available for the team to debug against).

"AWS S3 Compatible"

Uses AWS's S3 implementation as the reference behavior. (E.g., see AWS S3 API commands for the specific commands used.)

"AWS S3 compatible API" is defined as a storage system that complies with the behavior identified and tested as part of Dovecot Pro "AWS S3" Premium Support.

Microsoft Azure

Vendor website: Microsoft Azure

Microsoft's Azure blob storage API is supported.

DANGER

Microsoft Azure, as a public cloud service, requires authentication of every request.

Dovecot Pro has implemented User SAS authentication for the Blob Storage requests. Best efforts will be used to support this method, but testing may not occur for every Dovecot Pro release.

OX certifies that it will maintain support for at least one authentication system for Azure, but that system may change in the future based on vendor support and other considerations.

Release Notes will identify:

• The month & year we last tested against the Azure service
• The region where the testing occurred
• A link to the active documentation at the time testing occurred

NFS

WARNING

Dovecot Pro only supports NFS on installations with less than 250,000 users UNLESS specific additional NFS SLA support is added to the license.

Site replication is vendor-specific.

NFSv3 is known to work. NFSv4 will probably work, but the Dovecot team does not have any specific production information.

Storage/filesystem performance is not guaranteed.

Any NFS system is customer provided and not supported by OX.

OX cannot provide sizing information on NFS. If a customer wants sizing information, they should work with a storage vendor that has expertise.

OX can provide Professional Services support that can suggest optimizations, but these are non-binding recommendations specific to a customer and not general requirements.

Dictmap

For all object storage installations, Dictmap is REQUIRED.

CQL Storage

Dovecot stores and retrieves fs-dictmap information using CQL (Cassandra Query Language). CQL protocol version 4 is recommended and is the version that is currently tested against.

This database MUST be configured to be multi-node and highly available as part of Palomar.

Apache Cassandra

Website: Apache Cassandra

Apache Cassandra is the traditional service used with Dovecot, and has been successfully used in production in a variety of installations for many years.

OX tests at least one version of Apache Cassandra for every Pro release.

OX does not support configuration or operation of Cassandra. OX may provide Cassandra recommendations, but these are not binding. Support for Cassandra can be pursued through 3rd parties, such as DataStax.

Release Notes will identify:

• The specific version of Cassandra that was tested and confirmed working

ScyllaDB

NOTE

OX does not currently test against ScyllaDB. OX MAY include testing as part of the release process in future Dovecot Pro releases.

Website: ScyllaDB

ScyllaDB claims to be fully compatible with CQL protocol version 4. The customer is responsible for determining if this statement is accurate.

Dovecot Pro does not use or support any ScyllaDB extensions to the CQL protocol.

OX does not support configuration or operation of ScyllaDB. OX may provide ScyllaDB recommendations, but these are not binding. Support for ScyllaDB can be pursued through 3rd parties, such as via ScyllaDB.

Managed CQL Services

Various managed CQL services are available.

OX does not support configuration or operation of any specific managed services, and cannot provide recommendations or operational advice.

Mail Data Access

OX can only support mail data access if customer uses Dovecot provided APIs (i.e. Doveadm commands; scripts shipped with Pro packages).

OX CANNOT support direct modification of mail storage, for either NFS or object storage solutions.

doveadm-fs(1) commands can be used for debugging and fixing as instructed by Dovecot, but not as a regular way to access mails.