Add ability to test drive speeds on a MinIO setup (#7664)

- Extends existing Admin API to measure disk performance

pkg/disk/speedtest.go

@@ -0,0 +1,97 @@
+/*
+ * MinIO Cloud Storage, (C) 2019 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 disk
+
+import (
+	"io"
+	"math"
+	"time"
+
+	humanize "github.com/dustin/go-humanize"
+)
+
+var speedTestBlockSize = 4 * humanize.MiByte
+
+// speedTestWrite computes the write speed by writing
+// `speedTestFileSize` bytes of data to `w` in 4MiB direct-aligned
+// blocks present in `buf`
+func speedTestWrite(w io.Writer, buf []byte, size int64) (float64, error) {
+	// Write speedTestFileSize of data and record write speed
+	startTime := time.Now()
+	remaining := size
+	for remaining > 0 {
+		var toWrite int
+		// there's more remaining to write than the buffer can hold
+		if int64(len(buf)) < remaining {
+			toWrite = len(buf)
+		} else { // buffer can hold all there is to write
+			toWrite = int(remaining)
+		}
+
+		written, err := w.Write(buf[:toWrite])
+		if err != nil {
+			return 0, err
+		}
+
+		remaining = remaining - int64(written)
+	}
+
+	elapsedTime := time.Since(startTime).Seconds()
+	totalWriteMBs := float64(size) / humanize.MiByte
+	writeSpeed := totalWriteMBs / elapsedTime
+
+	return roundToTwoDecimals(writeSpeed), nil
+}
+
+// speedTestRead computes the read speed by reading
+// `speedTestFileSize` bytes from the reader `r` using 4MiB size `buf`
+func speedTestRead(r io.Reader, buf []byte, size int64) (float64, error) {
+	// Read speedTestFileSize and record read speed
+	startTime := time.Now()
+	remaining := size
+	for remaining > 0 {
+		// reads `speedTestBlockSize` on every read
+		n, err := io.ReadFull(r, buf)
+		if err == io.ErrUnexpectedEOF || err == nil {
+			remaining = remaining - int64(n)
+			continue
+		}
+
+		// Nothing more left to read from the Reader
+		if err == io.EOF {
+			break
+		}
+		// Error while reading from the underlying Reader
+		if err != nil {
+			return 0, err
+		}
+	}
+
+	if remaining > 0 {
+		return 0, io.ErrUnexpectedEOF
+	}
+
+	elapsedTime := time.Since(startTime).Seconds()
+	totalReadMBs := float64(size) / humanize.MiByte
+	readSpeed := totalReadMBs / elapsedTime
+
+	return roundToTwoDecimals(readSpeed), nil
+}
+
+func roundToTwoDecimals(num float64) float64 {
+	return math.Round(num*100) / 100
+}