feat: allow retaining parity SLA to be configurable (#19260)

at scale customers might start with failed drives,
causing skew in the overall usage ratio per EC set.

make this configurable such that customers can turn
this off as needed depending on how comfortable they
are.

cmd/erasure-multipart.go

@@ -401,36 +401,33 @@ func (er erasureObjects) newMultipartUpload(ctx context.Context, bucket string,
 		parityDrives = er.defaultParityCount
 	}
 
-	// If we have offline disks upgrade the number of erasure codes for this object.
-	parityOrig := parityDrives
+	if globalStorageClass.AvailabilityOptimized() {
+		// If we have offline disks upgrade the number of erasure codes for this object.
+		parityOrig := parityDrives
 
-	var offlineDrives int
-	for _, disk := range onlineDisks {
-		if disk == nil {
-			parityDrives++
-			offlineDrives++
-			continue
+		var offlineDrives int
+		for _, disk := range onlineDisks {
+			if disk == nil || !disk.IsOnline() {
+				parityDrives++
+				offlineDrives++
+				continue
+			}
 		}
-		if !disk.IsOnline() {
-			parityDrives++
-			offlineDrives++
-			continue
+
+		if offlineDrives >= (len(onlineDisks)+1)/2 {
+			// if offline drives are more than 50% of the drives
+			// we have no quorum, we shouldn't proceed just
+			// fail at that point.
+			return nil, toObjectErr(errErasureWriteQuorum, bucket, object)
 		}
-	}
 
-	if offlineDrives >= (len(onlineDisks)+1)/2 {
-		// if offline drives are more than 50% of the drives
-		// we have no quorum, we shouldn't proceed just
-		// fail at that point.
-		return nil, toObjectErr(errErasureWriteQuorum, bucket, object)
-	}
+		if parityDrives >= len(onlineDisks)/2 {
+			parityDrives = len(onlineDisks) / 2
+		}
 
-	if parityDrives >= len(onlineDisks)/2 {
-		parityDrives = len(onlineDisks) / 2
-	}
-
-	if parityOrig != parityDrives {
-		userDefined[minIOErasureUpgraded] = strconv.Itoa(parityOrig) + "->" + strconv.Itoa(parityDrives)
+		if parityOrig != parityDrives {
+			userDefined[minIOErasureUpgraded] = strconv.Itoa(parityOrig) + "->" + strconv.Itoa(parityDrives)
+		}
 	}
 
 	dataDrives := len(onlineDisks) - parityDrives

cmd/erasure-object.go

@@ -1297,25 +1297,21 @@ func (er erasureObjects) putObject(ctx context.Context, bucket string, object st
 
 	storageDisks := er.getDisks()
 
-	parityDrives := len(storageDisks) / 2
-	if !opts.MaxParity {
-		// Get parity and data drive count based on storage class metadata
-		parityDrives = globalStorageClass.GetParityForSC(userDefined[xhttp.AmzStorageClass])
-		if parityDrives < 0 {
-			parityDrives = er.defaultParityCount
-		}
-
+	// Get parity and data drive count based on storage class metadata
+	parityDrives := globalStorageClass.GetParityForSC(userDefined[xhttp.AmzStorageClass])
+	if parityDrives < 0 {
+		parityDrives = er.defaultParityCount
+	}
+	if opts.MaxParity {
+		parityDrives = len(storageDisks) / 2
+	}
+	if !opts.MaxParity && globalStorageClass.AvailabilityOptimized() {
 		// If we have offline disks upgrade the number of erasure codes for this object.
 		parityOrig := parityDrives
 
 		var offlineDrives int
 		for _, disk := range storageDisks {
-			if disk == nil {
-				parityDrives++
-				offlineDrives++
-				continue
-			}
-			if !disk.IsOnline() {
+			if disk == nil || !disk.IsOnline() {
 				parityDrives++
 				offlineDrives++
 				continue

internal/config/storageclass/help.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2015-2021 MinIO, Inc.
+// Copyright (c) 2015-2024 MinIO, Inc.
 //
 // This file is part of MinIO Object Storage stack
 //
@@ -38,6 +38,12 @@ var (
 			Optional:    true,
 			Type:        "string",
 		},
+		config.HelpKV{
+			Key:         ClassOptimize,
+			Description: `optimize parity calculation for standard storage class, set 'capacity' for capacity optimized (no additional parity)` + defaultHelpPostfix(ClassOptimize),
+			Optional:    true,
+			Type:        "string",
+		},
 		config.HelpKV{
 			Key:         config.Comment,
 			Description: config.DefaultComment,

internal/config/storageclass/storage-class.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2015-2021 MinIO, Inc.
+// Copyright (c) 2015-2024 MinIO, Inc.
 //
 // This file is part of MinIO Object Storage stack
 //
@@ -40,11 +40,14 @@ const (
 const (
 	ClassStandard = "standard"
 	ClassRRS      = "rrs"
+	ClassOptimize = "optimize"
 
 	// Reduced redundancy storage class environment variable
 	RRSEnv = "MINIO_STORAGE_CLASS_RRS"
 	// Standard storage class environment variable
 	StandardEnv = "MINIO_STORAGE_CLASS_STANDARD"
+	// Optimize storage class environment variable
+	OptimizeEnv = "MINIO_STORAGE_CLASS_OPTIMIZE"
 
 	// Supported storage class scheme is EC
 	schemePrefix = "EC"
@@ -67,6 +70,10 @@ var (
 			Key:   ClassRRS,
 			Value: "EC:1",
 		},
+		config.KV{
+			Key:   ClassOptimize,
+			Value: "availability",
+		},
 	}
 )
 
@@ -82,6 +89,7 @@ var ConfigLock sync.RWMutex
 type Config struct {
 	Standard    StorageClass `json:"standard"`
 	RRS         StorageClass `json:"rrs"`
+	Optimize    string       `json:"optimize"`
 	initialized bool
 }
 
@@ -245,12 +253,40 @@ func (sCfg *Config) GetParityForSC(sc string) (parity int) {
 	}
 }
 
+// CapacityOptimized - returns true if the storage-class is capacity optimized
+// meaning we will not use additional parities when drives are offline.
+//
+// Default is "availability" optimized, unless this is configured.
+func (sCfg *Config) CapacityOptimized() bool {
+	ConfigLock.RLock()
+	defer ConfigLock.RUnlock()
+	if !sCfg.initialized {
+		return false
+	}
+	return sCfg.Optimize == "capacity"
+}
+
+// AvailabilityOptimized - returns true if the storage-class is availability
+// optimized, meaning we will use additional parities when drives are offline
+// to retain parity SLA.
+//
+// Default is "availability" optimized.
+func (sCfg *Config) AvailabilityOptimized() bool {
+	ConfigLock.RLock()
+	defer ConfigLock.RUnlock()
+	if !sCfg.initialized {
+		return true
+	}
+	return sCfg.Optimize == "availability" || sCfg.Optimize == ""
+}
+
 // Update update storage-class with new config
 func (sCfg *Config) Update(newCfg Config) {
 	ConfigLock.Lock()
 	defer ConfigLock.Unlock()
 	sCfg.RRS = newCfg.RRS
 	sCfg.Standard = newCfg.Standard
+	sCfg.Optimize = newCfg.Optimize
 	sCfg.initialized = true
 }
 
@@ -320,5 +356,6 @@ func LookupConfig(kvs config.KVS, setDriveCount int) (cfg Config, err error) {
 	}
 
 	cfg.initialized = true
+	cfg.Optimize = env.Get(OptimizeEnv, kvs.Get(ClassOptimize))
 	return cfg, nil
 }