fix: speed up drive mux registration (#12319)

in setups with lots of drives the server
startup is slow, initialize all local drives
in parallel before registering with muxer.

this speeds up when there are multiple pools
and large collection of drives.

cmd/storage-rest-server.go

@@ -31,6 +31,7 @@ import (
 	"path"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/tinylib/msgp/msgp"
@@ -1003,18 +1004,39 @@ func logFatalErrs(err error, endpoint Endpoint, exit bool) {
 
 // registerStorageRPCRouter - register storage rpc router.
 func registerStorageRESTHandlers(router *mux.Router, endpointServerPools EndpointServerPools) {
-	for _, ep := range endpointServerPools {
+	storageDisks := make([][]*xlStorage, len(endpointServerPools))
-		for _, endpoint := range ep.Endpoints {
+	for poolIdx, ep := range endpointServerPools {
+		storageDisks[poolIdx] = make([]*xlStorage, len(ep.Endpoints))
+	}
+	var wg sync.WaitGroup
+	for poolIdx, ep := range endpointServerPools {
+		for setIdx, endpoint := range ep.Endpoints {
 			if !endpoint.IsLocal {
 				continue
 			}
-			storage, err := newXLStorage(endpoint)
+			wg.Add(1)
-			if err != nil {
+			go func(poolIdx, setIdx int, endpoint Endpoint) {
-				// if supported errors don't fail, we proceed to
+				defer wg.Done()
-				// printing message and moving forward.
+				var err error
-				logFatalErrs(err, endpoint, false)
+				storageDisks[poolIdx][setIdx], err = newXLStorage(endpoint)
+				if err != nil {
+					// if supported errors don't fail, we proceed to
+					// printing message and moving forward.
+					logFatalErrs(err, endpoint, false)
+				}
+			}(poolIdx, setIdx, endpoint)
+		}
+	}
+	wg.Wait()
+
+	for _, setDisks := range storageDisks {
+		for _, storage := range setDisks {
+			if storage == nil {
+				continue
 			}
 
+			endpoint := storage.Endpoint()
+
 			server := &storageRESTServer{storage: storage}
 
 			subrouter := router.PathPrefix(path.Join(storageRESTPrefix, endpoint.Path)).Subrouter()