minio/docs/compression

Compression Guide

For SILO's current SSE-C compression and historical-object boundary, see the maintained encryption guide and SSE-C replica design. Check the documented release boundary before applying main-branch behavior to an older binary.

Silo server allows streaming compression to ensure efficient disk space usage. Compression happens inflight, i.e objects are compressed before being written to disk(s). Silo uses klauspost/compress/s2 streaming compression due to its stability and performance.

This algorithm is specifically optimized for machine generated content. Write throughput is typically at least 500MB/s per CPU core, and scales with the number of available CPU cores. Decompression speed is typically at least 1GB/s.

This means that in cases where raw IO is below these numbers compression will not only reduce disk usage but also help increase system throughput. Typically, enabling compression on spinning disk systems will increase speed when the content can be compressed.

Get Started

1. Prerequisites

Install Silo - Silo Quickstart Guide.

2. Run Silo with compression

Compression can be enabled by updating the compress config settings for Silo server config. Config compress settings take extensions and mime-types to be compressed.

~ mc admin config get mysilo compression
compression extensions=".txt,.log,.csv,.json,.tar,.xml,.bin" mime_types="text/*,application/json,application/xml"

Default config includes most common highly compressible content extensions and mime-types.

~ mc admin config set mysilo compression extensions=".pdf" mime_types="application/pdf"

To show help on setting compression config values.

~ mc admin config set mysilo compression

To enable compression for all content, no matter the extension and content type (except for the default excluded types) set BOTH extensions and mime types to empty.

~ mc admin config set mysilo compression enable="on" extensions="" mime_types=""

The compression settings may also be set through environment variables. When set, environment variables override the defined compress config settings in the server config.

export MINIO_COMPRESSION_ENABLE="on"
export MINIO_COMPRESSION_EXTENSIONS=".txt,.log,.csv,.json,.tar,.xml,.bin"
export MINIO_COMPRESSION_MIME_TYPES="text/*,application/json,application/xml"

Note

To enable compression for all content when using environment variables, set either or both of the extensions and MIME types to * instead of an empty string:

export MINIO_COMPRESSION_ENABLE="on"
export MINIO_COMPRESSION_EXTENSIONS="*"
export MINIO_COMPRESSION_MIME_TYPES="*"

3. Compression + Encryption

Combining encryption and compression is not safe in all setups. This is particularly so if the compression ratio of your content reveals information about it. See CRIME TLS as an example of this.

Therefore, compression is disabled when encrypting by default, and must be enabled separately.

Evaluate the security and resource impact in a staging environment before deciding whether this feature combination is safe for your setup.

To enable compression+encryption use:

~ mc admin config set mysilo compression allow_encryption=on

Or alternatively through the environment variable MINIO_COMPRESSION_ALLOW_ENCRYPTION=on.

SSE-C objects are excluded from compression even with allow_encryption=on. Replication ships an SSE-C object as raw ciphertext, because the server never holds the customer key, and the compression metadata is not carried over the wire. A compressed SSE-C object would therefore replicate to a replica that decrypts to a compressed stream. allow_encryption still applies to SSE-S3 and SSE-KMS, where the server owns the key and decompresses before replicating.

4. Excluded Types

• Already compressed objects are not fit for compression since they do not have compressible patterns. Such objects do not produce efficient LZ compression which is a fitness factor for a lossless data compression.

Pre-compressed input typically compresses in excess of 2GiB/s per core, so performance impact should be minimal even if precompressed data is re-compressed. Decompressing incompressible data has no significant performance impact.

Below is a list of common files and content-types which are typically not suitable for compression.

• Extensions

| gz | (GZIP) | | bz2 | (BZIP2) | | rar | (WinRAR) | | zip | (ZIP) | | 7z | (7-Zip) | | xz | (LZMA) | | mp4 | (MP4) | | mkv | (MKV media) | | mov | (MOV) |

• Content-Types

| video/* | | audio/* | | application/zip | | application/x-gzip | | application/zip | | application/x-bz2 | | application/x-compress | | application/x-xz |

All files with these extensions and mime types are excluded from compression, even if compression is enabled for all types.

To test the setup

To test this setup, practice put calls to the server using mc and use mc ls on the data directory to view the size of the object.

Explore Further

• Use mc with Silo Server
• Use aws-cli with Silo Server
• Use minio-go SDK with Silo Server
• The Silo documentation website