Deprecate caching for erasure/distributed mode (#13909)

Fixes: #13907

Also removing default value of `writethrough` for cache commit
which was interfering with cache_after setting

cmd/disk-cache.go

@@ -706,7 +706,7 @@ func (c *cacheObjects) PutObject(ctx context.Context, bucket, object string, r *
 				oi, _, err := dcache.Stat(GlobalContext, bucket, object)
 				// avoid cache overwrite if another background routine filled cache
 				if err != nil || oi.ETag != bReader.ObjInfo.ETag {
-					dcache.Put(GlobalContext, bucket, object, bReader, bReader.ObjInfo.Size, nil, ObjectOptions{UserDefined: getMetadata(bReader.ObjInfo)}, false, true)
+					dcache.Put(GlobalContext, bucket, object, bReader, bReader.ObjInfo.Size, nil, ObjectOptions{UserDefined: getMetadata(bReader.ObjInfo)}, false, false)
 				}
 			}()
 		}

cmd/server-main.go

@@ -591,8 +591,9 @@ func serverMain(ctx *cli.Context) {
 		}
 	}
 
+	// initialize the new disk cache objects.
 	if globalCacheConfig.Enabled {
-		// initialize the new disk cache objects.
+		logStartupMessage(color.Yellow("WARNING: Disk caching is deprecated for single/multi drive MinIO setups. Please migrate to using MinIO S3 gateway instead of disk caching"))
 		var cacheAPI CacheObjectLayer
 		cacheAPI, err = newServerCacheObjects(GlobalContext, globalCacheConfig)
 		logger.FatalIf(err, "Unable to initialize disk caching")

internal/config/cache/lookup.go

@@ -56,7 +56,6 @@ const (
 	DefaultAfter         = "0"
 	DefaultWaterMarkLow  = "70"
 	DefaultWaterMarkHigh = "80"
-	DefaultCacheCommit   = WriteThrough
 )
 
 // DefaultKVS - default KV settings for caching.
@@ -96,7 +95,7 @@ var (
 		},
 		config.KV{
 			Key:   Commit,
-			Value: DefaultCacheCommit,
+			Value: "",
 		},
 	}
 )