minio/docs/erasure/storage-class

Minio Storage Class Quickstart Guide

Minio server supports storage class in erasure coding mode. This allows configurable data and parity disks per object.

Overview

Minio supports two storage classes, Reduced Redundancy class and Standard class. These classes can be defined using environment variables set before starting Minio server. After the data and parity disks for each storage class are defined using environment variables, you can set the storage class of an object via request metadata field x-amz-storage-class. Minio server then honors the storage class by saving the object in specific number of data and parity disks.

Values for standard storage class (STANDARD)

STANDARD storage class implies more parity than REDUCED_REDUNDANCY class. So, STANDARD parity disks should be

• Greater than or equal to 2, if REDUCED_REDUNDANCY parity is not set.
• Greater than REDUCED_REDUNDANCY parity, if it is set.

Parity blocks can not be higher than data blocks, so STANDARD storage class parity can not be higher than N/2. (N being total number of disks)

Default value for STANDARD storage class is N/2 (N is the total number of drives).

Values for reduced redundancy storage class (REDUCED_REDUNDANCY)

REDUCED_REDUNDANCY implies lesser parity than STANDARD class. So,REDUCED_REDUNDANCY parity disks should be

• Less than N/2, if STANDARD parity is not set.
• Less than STANDARD Parity, if it is set.

As parity below 2 is not recommended, REDUCED_REDUNDANCY storage class is not supported for 4 disks erasure coding setup.

Default value for REDUCED_REDUNDANCY storage class is 2.

Get started with Storage Class

Set storage class

The format to set storage class environment variables is as follows

MINIO_STORAGE_CLASS_STANDARD=EC:parity MINIO_STORAGE_CLASS_RRS=EC:parity

For example, set MINIO_STORAGE_CLASS_RRS parity 2 and MINIO_STORAGE_CLASS_STANDARD parity 3

export MINIO_STORAGE_CLASS_STANDARD=EC:3
export MINIO_STORAGE_CLASS_RRS=EC:2

Storage class can also be set via config.json file. Refer storage class for more details.

Note

• If STANDARD storage class is set via environment variables or config.json files, and x-amz-storage-class is not present in request metadata, Minio server will apply STANDARD storage class to the object. This means the data and parity disks will be used as set in STANDARD storage class.

• If storage class is not defined before starting Minio server, and subsequent PutObject metadata field has x-amz-storage-class present with values REDUCED_REDUNDANCY or STANDARD, Minio server uses default parity values.

Set metadata

In below example minio-go is used to set the storage class to REDUCED_REDUNDANCY. This means this object will be split across 6 data disks and 2 parity disks (as per the storage class set in previous step).

s3Client, err := minio.New("localhost:9000", "YOUR-ACCESSKEYID", "YOUR-SECRETACCESSKEY", true)
if err != nil {
	log.Fatalln(err)
}

object, err := os.Open("my-testfile")
if err != nil {
	log.Fatalln(err)
}
defer object.Close()
objectStat, err := object.Stat()
if err != nil {
	log.Fatalln(err)
}

n, err := s3Client.PutObject("my-bucketname", "my-objectname", object, objectStat.Size(), minio.PutObjectOptions{ContentType: "application/octet-stream", StorageClass: "REDUCED_REDUNDANCY"})
if err != nil {
	log.Fatalln(err)
}
log.Println("Uploaded", "my-objectname", " of size: ", n, "Successfully.")