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minio/cmd/storage-class.go

234 lines
8.0 KiB

/*
* Minio Cloud Storage, (C) 2017 Minio, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package cmd
import (
"errors"
"fmt"
"strconv"
"strings"
)
const (
// metadata entry for storage class
amzStorageClass = "x-amz-storage-class"
// Canonical metadata entry for storage class
amzStorageClassCanonical = "X-Amz-Storage-Class"
// Reduced redundancy storage class
reducedRedundancyStorageClass = "REDUCED_REDUNDANCY"
// Standard storage class
standardStorageClass = "STANDARD"
// Reduced redundancy storage class environment variable
reducedRedundancyStorageClassEnv = "MINIO_STORAGE_CLASS_RRS"
// Standard storage class environment variable
standardStorageClassEnv = "MINIO_STORAGE_CLASS_STANDARD"
// Supported storage class scheme is EC
supportedStorageClassScheme = "EC"
// Minimum parity disks
minimumParityDisks = 2
defaultRRSParity = 2
)
// Struct to hold storage class
type storageClass struct {
Scheme string
Parity int
}
type storageClassConfig struct {
Standard storageClass `json:"standard"`
RRS storageClass `json:"rrs"`
}
// Validate if storage class in metadata
// Only Standard and RRS Storage classes are supported
func isValidStorageClassMeta(sc string) bool {
return sc == reducedRedundancyStorageClass || sc == standardStorageClass
}
func (sc *storageClass) UnmarshalText(b []byte) error {
scStr := string(b)
if scStr != "" {
s, err := parseStorageClass(scStr)
if err != nil {
return err
}
sc.Parity = s.Parity
sc.Scheme = s.Scheme
} else {
sc = &storageClass{}
}
return nil
}
func (sc *storageClass) MarshalText() ([]byte, error) {
if sc.Scheme != "" && sc.Parity != 0 {
return []byte(fmt.Sprintf("%s:%d", sc.Scheme, sc.Parity)), nil
}
return []byte(""), nil
}
// Parses given storageClassEnv and returns a storageClass structure.
// Supported Storage Class format is "Scheme:Number of parity disks".
// Currently only supported scheme is "EC".
func parseStorageClass(storageClassEnv string) (sc storageClass, err error) {
s := strings.Split(storageClassEnv, ":")
// only two elements allowed in the string - "scheme" and "number of parity disks"
if len(s) > 2 {
return storageClass{}, errors.New("Too many sections in " + storageClassEnv)
} else if len(s) < 2 {
return storageClass{}, errors.New("Too few sections in " + storageClassEnv)
}
// only allowed scheme is "EC"
if s[0] != supportedStorageClassScheme {
return storageClass{}, errors.New("Unsupported scheme " + s[0] + ". Supported scheme is EC")
}
// Number of parity disks should be integer
parityDisks, err := strconv.Atoi(s[1])
if err != nil {
return storageClass{}, err
}
sc = storageClass{
Scheme: s[0],
Parity: parityDisks,
}
return sc, nil
}
// Validates the parity disks for Reduced Redundancy storage class
func validateRRSParity(rrsParity, ssParity int) (err error) {
disks := len(globalEndpoints)
// disks < 4 means this is not a erasure coded setup and so storage class is not supported
if disks < 4 {
return fmt.Errorf("Setting storage class only allowed for erasure coding mode")
}
// Reduced redundancy storage class is not supported for 4 disks erasure coded setup.
if disks == 4 && rrsParity != 0 {
return fmt.Errorf("Reduced redundancy storage class not supported for " + strconv.Itoa(disks) + " disk setup")
}
// RRS parity disks should be greater than or equal to minimumParityDisks. Parity below minimumParityDisks is not recommended.
if rrsParity < minimumParityDisks {
return fmt.Errorf("Reduced redundancy storage class parity should be greater than or equal to " + strconv.Itoa(minimumParityDisks))
}
// Reduced redundancy implies lesser parity than standard storage class. So, RRS parity disks should be
// - less than N/2, if StorageClass parity is not set.
// - less than StorageClass Parity, if Storage class parity is set.
switch ssParity {
case 0:
if rrsParity >= disks/2 {
return fmt.Errorf("Reduced redundancy storage class parity disks should be less than " + strconv.Itoa(disks/2))
}
default:
if rrsParity >= ssParity {
return fmt.Errorf("Reduced redundancy storage class parity disks should be less than " + strconv.Itoa(ssParity))
}
}
return nil
}
// Validates the parity disks for Standard storage class
func validateSSParity(ssParity, rrsParity int) (err error) {
disks := len(globalEndpoints)
// disks < 4 means this is not a erasure coded setup and so storage class is not supported
if disks < 4 {
return fmt.Errorf("Setting storage class only allowed for erasure coding mode")
}
// Standard storage class implies more parity than Reduced redundancy storage class. So, Standard storage parity disks should be
// - greater than or equal to 2, if RRS parity is not set.
// - greater than RRS Parity, if RRS parity is set.
switch rrsParity {
case 0:
if ssParity < minimumParityDisks {
return fmt.Errorf("Standard storage class parity disks should be greater than or equal to " + strconv.Itoa(minimumParityDisks))
}
default:
if ssParity <= rrsParity {
return fmt.Errorf("Standard storage class parity disks should be greater than " + strconv.Itoa(rrsParity))
}
}
// Standard storage class parity should be less than or equal to N/2
if ssParity > disks/2 {
return fmt.Errorf("Standard storage class parity disks should be less than or equal to " + strconv.Itoa(disks/2))
}
return nil
}
// Returns the data and parity drive count based on storage class
// If storage class is set using the env vars MINIO_STORAGE_CLASS_RRS and MINIO_STORAGE_CLASS_STANDARD
// or config.json fields
// -- corresponding values are returned
// If storage class is not set during startup, default values are returned
// -- Default for Reduced Redundancy Storage class is, parity = 2 and data = N-Parity
// -- Default for Standard Storage class is, parity = N/2, data = N/2
// If storage class is empty
// -- standard storage class is assumed and corresponding data and parity is returned
func getRedundancyCount(sc string, totalDisks int) (data, parity int) {
parity = totalDisks / 2
switch sc {
case reducedRedundancyStorageClass:
if globalRRStorageClass.Parity != 0 {
// set the rrs parity if available
parity = globalRRStorageClass.Parity
} else {
// else fall back to default value
parity = defaultRRSParity
}
case standardStorageClass, "":
if globalStandardStorageClass.Parity != 0 {
// set the standard parity if available
parity = globalStandardStorageClass.Parity
}
}
// data is always totalDisks - parity
return totalDisks - parity, parity
}
// Returns per object readQuorum and writeQuorum
// readQuorum is the minimum required disks to read data.
// writeQuorum is the minimum required disks to write data.
func objectQuorumFromMeta(xl xlObjects, partsMetaData []xlMetaV1, errs []error) (objectReadQuorum, objectWriteQuorum int, err error) {
// get the latest updated Metadata and a count of all the latest updated xlMeta(s)
latestXLMeta, count := getLatestXLMeta(partsMetaData, errs)
// latestXLMeta is updated most recently.
// We implicitly assume that all the xlMeta(s) have same dataBlocks and parityBlocks.
// We now check that at least dataBlocks number of xlMeta is available. This means count
// should be greater than or equal to dataBlocks field of latestXLMeta. If not we throw read quorum error.
if count < latestXLMeta.Erasure.DataBlocks {
// This is the case when we can't reliably deduce object quorum
return 0, 0, errXLReadQuorum
}
// Since all the valid erasure code meta updated at the same time are equivalent, pass dataBlocks
// from latestXLMeta to get the quorum
return latestXLMeta.Erasure.DataBlocks, latestXLMeta.Erasure.DataBlocks + 1, nil
}