choose starting concurrency based on number of local disks (#15428)

smaller setups may have less drives per server choosing
the concurrency based on number of local drives, and let
the MinIO server change the overall concurrency as
necessary.

cmd/endpoint.go

@@ -292,6 +292,19 @@ func (l EndpointServerPools) LocalDisksPaths() []string {
 	return disks
 }
 
+// NLocalDisksPathsPerPool returns the disk paths of the local disks per pool
+func (l EndpointServerPools) NLocalDisksPathsPerPool() []int {
+	localDisksCount := make([]int, len(l))
+	for i, ep := range l {
+		for _, endpoint := range ep.Endpoints {
+			if endpoint.IsLocal {
+				localDisksCount[i]++
+			}
+		}
+	}
+	return localDisksCount
+}
+
 // FirstLocal returns true if the first endpoint is local.
 func (l EndpointServerPools) FirstLocal() bool {
 	return l[0].Endpoints[0].IsLocal