diff --git a/cmd/mrf.go b/cmd/mrf.go
index 60c302d2b..7eccda884 100644
--- a/cmd/mrf.go
+++ b/cmd/mrf.go
@@ -47,7 +47,7 @@ type mrfState struct {
 	ctx   context.Context
 	pools *erasureServerPools
 
-	mu   sync.Mutex
+	mu   sync.RWMutex
 	opCh chan partialOperation
 }
 
@@ -72,6 +72,9 @@ func (m *mrfState) addPartialOp(op partialOperation) {
 		return
 	}
 
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+
 	select {
 	case m.opCh <- op:
 	default:
diff --git a/cmd/xl-storage-disk-id-check.go b/cmd/xl-storage-disk-id-check.go
index f85578291..bb1ee7e91 100644
--- a/cmd/xl-storage-disk-id-check.go
+++ b/cmd/xl-storage-disk-id-check.go
@@ -209,9 +209,24 @@ func newXLStorageDiskIDCheck(storage *xlStorage, healthCheck bool) *xlStorageDis
 	})
 
 	if driveMaxConcurrent <= 0 {
-		driveMaxConcurrent = 512
+		// nr_requests is for both READ and WRITE separately
+		// so we this 2x tokens on our end.
+		//
+		// https://www.kernel.org/doc/Documentation/block/queue-sysfs.txt
+		//
+		// nr_requests (RW)
+		// ----------------
+		// This controls how many requests may be allocated in the block layer for
+		// read or write requests. Note that the total allocated number may be twice
+		// this amount, since it applies only to reads or writes (not the accumulated
+		// sum).
+		driveMaxConcurrent = int(storage.nrRequests) * 2
+		if driveMaxConcurrent <= 0 {
+			driveMaxConcurrent = 1023 * 2 // Default value on Linux for most NVMe
+		}
 		if storage.rotational {
-			driveMaxConcurrent = int(storage.nrRequests) / 2
+			// use 80% of the available nr_requests on HDDs
+			driveMaxConcurrent = int(float64(storage.nrRequests)*0.8) * 2
 			if driveMaxConcurrent < 32 {
 				driveMaxConcurrent = 32
 			}