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112 lines
5.3 KiB
Markdown
112 lines
5.3 KiB
Markdown
# MinIO Storage Class Quickstart Guide [](https://slack.min.io)
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MinIO server supports storage class in erasure coding mode. This allows configurable data and parity disks per object.
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## Overview
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MinIO supports two storage classes, Reduced Redundancy class and Standard class. These classes can be defined using environment variables
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set before starting MinIO server. After the data and parity disks for each storage class are defined using environment variables,
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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
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saving the object in specific number of data and parity disks.
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## Storage usage
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The selection of varying data and parity drives has a direct impact on the drive space usage. With storage class, you can optimize for high
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redundancy or better drive space utilization.
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To get an idea of how various combinations of data and parity drives affect the storage usage, let’s take an example of a 100 MiB file stored
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on 16 drive MinIO deployment. If you use eight data and eight parity drives, the file space usage will be approximately twice, i.e. 100 MiB
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file will take 200 MiB space. But, if you use ten data and six parity drives, same 100 MiB file takes around 160 MiB. If you use 14 data and
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two parity drives, 100 MiB file takes only approximately 114 MiB.
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Below is a list of data/parity drives and corresponding _approximate_ storage space usage on a 16 drive MinIO deployment. The field _storage
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usage ratio_ is simply the drive space used by the file after erasure-encoding, divided by actual file size.
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| Total Drives (N) | Data Drives (D) | Parity Drives (P) | Storage Usage Ratio |
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|------------------|-----------------|-------------------|---------------------|
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| 16 | 8 | 8 | 2.00 |
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| 16 | 9 | 7 | 1.79 |
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| 16 | 10 | 6 | 1.60 |
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| 16 | 11 | 5 | 1.45 |
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| 16 | 12 | 4 | 1.34 |
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| 16 | 13 | 3 | 1.23 |
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| 16 | 14 | 2 | 1.14 |
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You can calculate _approximate_ storage usage ratio using the formula - total drives (N) / data drives (D).
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### Allowed values for STANDARD storage class
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`STANDARD` storage class implies more parity than `REDUCED_REDUNDANCY` class. So, `STANDARD` parity disks should be
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- Greater than or equal to 2, if `REDUCED_REDUNDANCY` parity is not set.
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- Greater than `REDUCED_REDUNDANCY` parity, if it is set.
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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)
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Default value for `STANDARD` storage class is `N/2` (N is the total number of drives).
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### Allowed values for REDUCED_REDUNDANCY storage class
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`REDUCED_REDUNDANCY` implies lesser parity than `STANDARD` class. So,`REDUCED_REDUNDANCY` parity disks should be
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- Less than N/2, if `STANDARD` parity is not set.
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- Less than `STANDARD` Parity, if it is set.
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As parity below 2 is not recommended, `REDUCED_REDUNDANCY` storage class is not supported for 4 disks erasure coding setup.
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Default value for `REDUCED_REDUNDANCY` storage class is `2`.
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## Get started with Storage Class
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### Set storage class
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The format to set storage class environment variables is as follows
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`MINIO_STORAGE_CLASS_STANDARD=EC:parity`
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`MINIO_STORAGE_CLASS_RRS=EC:parity`
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For example, set `MINIO_STORAGE_CLASS_RRS` parity 2 and `MINIO_STORAGE_CLASS_STANDARD` parity 3
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```sh
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export MINIO_STORAGE_CLASS_STANDARD=EC:3
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export MINIO_STORAGE_CLASS_RRS=EC:2
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```
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Storage class can also be set via `mc admin config` get/set commands to update the configuration. Refer [storage class](https://github.com/minio/minio/tree/master/docs/config#storage-class) for
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more details.
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*Note*
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- If `STANDARD` storage class is set via environment variables or `mc admin config` get/set commands, and `x-amz-storage-class` is not present in request metadata, MinIO server will
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apply `STANDARD` storage class to the object. This means the data and parity disks will be used as set in `STANDARD` storage class.
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- If storage class is not defined before starting MinIO server, and subsequent PutObject metadata field has `x-amz-storage-class` present
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with values `REDUCED_REDUNDANCY` or `STANDARD`, MinIO server uses default parity values.
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### Set metadata
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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).
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```go
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s3Client, err := minio.New("localhost:9000", "YOUR-ACCESSKEYID", "YOUR-SECRETACCESSKEY", true)
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if err != nil {
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log.Fatalln(err)
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}
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object, err := os.Open("my-testfile")
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if err != nil {
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log.Fatalln(err)
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}
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defer object.Close()
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objectStat, err := object.Stat()
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if err != nil {
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log.Fatalln(err)
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}
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n, err := s3Client.PutObject("my-bucketname", "my-objectname", object, objectStat.Size(), minio.PutObjectOptions{ContentType: "application/octet-stream", StorageClass: "REDUCED_REDUNDANCY"})
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if err != nil {
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log.Fatalln(err)
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}
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log.Println("Uploaded", "my-objectname", " of size: ", n, "Successfully.")
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```
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