diff --git a/src/bio/SConscript b/src/bio/SConscript
index 88211d8eaf1..fca897e5f33 100644
--- a/src/bio/SConscript
+++ b/src/bio/SConscript
@@ -23,6 +23,8 @@ def scons():
     denv.AppendUnique(OBJPREFIX='b_')
 
     # SPDK related libs
+    # libbio.so 依赖spdk 的库
+    # 所在目录:/opt/daos/prereq/release/spdk/lib# ll *.so
     libs = ['spdk_log', 'spdk_env_dpdk', 'spdk_thread', 'spdk_bdev', 'rte_mempool']
     libs += ['rte_mempool_ring', 'rte_bus_pci', 'rte_pci', 'rte_ring']
     libs += ['rte_mbuf', 'rte_eal', 'rte_kvargs', 'spdk_bdev_aio']
diff --git a/src/bio/bio_xstream.c b/src/bio/bio_xstream.c
index 8226cf975c9..731ad287802 100644
--- a/src/bio/bio_xstream.c
+++ b/src/bio/bio_xstream.c
@@ -100,6 +100,7 @@ static struct bio_nvme_data nvme_glb;
 static int
 bio_spdk_env_init(void)
 {
+	// 构建spdk opt
 	struct spdk_env_opts	opts;
 	bool			enable_rpc_srv = false;
 	int			rc;
@@ -123,6 +124,7 @@ bio_spdk_env_init(void)
 	// == true
 	if (bio_nvme_configured(SMD_DEV_TYPE_MAX)) {
 		// 传递allowed bdev pci 地址给spdk，即将nvme addr 添加到opts 的allowlist 中
+		// nvme 类型的bdev，创建命令是conf 中的 attach controller
 		rc = bio_add_allowed_alloc(nvme_glb.bd_nvme_conf, &opts, &roles);
 		if (rc != 0) {
 			D_ERROR("Failed to add allowed devices to SPDK env, "DF_RC"\n",
@@ -483,6 +485,7 @@ struct common_cp_arg {
 static void
 common_prep_arg(struct common_cp_arg *arg)
 {
+	// 设置一个 inflight
 	arg->cca_inflights = 1;
 	arg->cca_rc = 0;
 	arg->cca_bs = NULL;
@@ -491,6 +494,7 @@ common_prep_arg(struct common_cp_arg *arg)
 static void
 common_init_cb(void *arg, int rc)
 {
+	// rpc 执行成功或者超时后，inflight 自减
 	struct common_cp_arg *cp_arg = arg;
 
 	D_ASSERT(cp_arg->cca_inflights == 1);
@@ -1732,13 +1736,17 @@ bio_xsctxt_alloc(struct bio_xs_context **pctxt, int tgt_id, bool self_polling)
 		common_prep_arg(&cp_arg);
 		// 这里用的是全局的nvme conf 文件，每个engine 有自己单独的
 		// spdk 中子系统其实就是模块的意思，比如子系统名字为bdev，表示bdev 模块
+		// 这里面会调用 spdk_rpc_initialize，会启动rpc 服务监听
 		spdk_subsystem_init_from_json_config(nvme_glb.bd_nvme_conf,
 						     SPDK_DEFAULT_RPC_ADDR,
 						     subsys_init_cb, &cp_arg,
 						     true);
+		// init from json 会注册 rpc_subsystem_poll，rpc_client_connect_poller，用于接收rpc 请求
+		// 这里是为了等待rpc req 被处理完，或者req 超时
 		rc = xs_poll_completion(ctxt, &cp_arg.cca_inflights, 0);
 		D_ASSERT(rc == 0);
 
+		// 初始化失败了
 		if (cp_arg.cca_rc != 0) {
 			rc = cp_arg.cca_rc;
 			D_ERROR("failed to init bdevs, rc:%d\n", rc);
@@ -1746,14 +1754,21 @@ bio_xsctxt_alloc(struct bio_xs_context **pctxt, int tgt_id, bool self_polling)
 		}
 
 		/* Continue poll until no more events */
-		// todo: 这里是为啥
+		// 这个时间点:
+		// 1. 不会有其他xs，所有没人给这个 init_thread 通过 spdk_thread_send_msg 发meg
+		// 2. 所以只能是处理已经注册过的poller：rpc_subsystem_poll，rpc_client_connect_poller
+		// 1-1: spdk_subsystem_init_from_json_config --> spdk_rpc_initialize --> rpc_subsystem_poll --> spdk_rpc_accept  ---> spdk_jsonrpc_server_poll: 检查监听的socket，处理连接
+		// 2-2: spdk_subsystem_init_from_json_config --> rpc_client_connect_poller --> spdk_jsonrpc_client_poll  --> jsonrpc_client_poll / jsonrpc_client_poll_connecting
+		//  return 1 if work was done. 0 if no work was done.
+		// 返回0表示轮询成功，但是没有处理任何事件；返回>0 表示轮询成功，且处理了n 个事件；返回 <0 表示轮询失败
+		// 这里是loop 直到所有的事件都被处理完
 		while (spdk_thread_poll(ctxt->bxc_thread, 0, 0) > 0)
 			;
 		// 这个日志会打印，tgt_id 为 0
-		// todo: 什么样才算初始化完成，此时可以通过 spdk_bdev_first 拿到spdk bdev 了吗？
+		// 初始化完成，此时可以通过 spdk_bdev_first 拿到spdk bdev 了
 		D_DEBUG(DB_MGMT, "SPDK bdev initialized, tgt_id:%d", tgt_id);
 
-		// 将spdk thread 设置到全局数据中，表示在众多（每个xs 有各自的spdk thread）的thread 中，当前是扫描bdev那个
+		// 将spdk thread 设置到全局数据中，表示在众多（每个xs 有各自的spdk thread）的thread 中，当前是初始化的那个
 		nvme_glb.bd_init_thread = ctxt->bxc_thread;
 	
 		// 内部会load_blobstore 最终创建spdk bs，只有target 0 会执行
@@ -1764,7 +1779,10 @@ bio_xsctxt_alloc(struct bio_xs_context **pctxt, int tgt_id, bool self_polling)
 			goto out;
 		}
 
-		// bio bdev 初始化完成后，重启spdk rpc server。rpc 默认是禁用的
+		// 上面 spdk_subsystem_init_from_json_config 中会通过调用 spdk_rpc_initialize 自动开启rpc 监听
+		// 用于处理json 文件中配置的method，其中 nvme_attach_controller 会1. 创建nvme ctrlr 2. 添加ns 到nvme ctrlr 3. 注册spdk nvme bdev
+		// 在 init_bio_bdevs 函数执行之前，spdk nvme bdev 注册已经完成（通过nvme_attach_controller 对应的mapping 函数，走的rpc 流程）
+		// 当 bio bdev 初始化完成后，重启spdk rpc server，这里是false，所以不用重启
 		/* After bio_bdevs are initialized, restart SPDK JSON-RPC server if required. */
 		// 默认是false
 		if (nvme_glb.bd_enable_rpc_srv) {
diff --git a/src/control/cmd/daos_server_helper/handler.go b/src/control/cmd/daos_server_helper/handler.go
index c80e5509e30..6e900f4ec77 100644
--- a/src/control/cmd/daos_server_helper/handler.go
+++ b/src/control/cmd/daos_server_helper/handler.go
@@ -230,7 +230,6 @@ type bdevHandler struct {
 	bdevProvider *bdev.Provider
 }
 
-// todo: provider 怎么理解
 func (h *bdevHandler) setupProvider(log logging.Logger) {
 	if h.bdevProvider == nil {
 		// 调用了bdev 包下的 DefaultProvider。对应的后端是 spdkbackend
@@ -257,6 +256,7 @@ func (h *bdevScanHandler) Handle(log logging.Logger, req *pbin.Request) *pbin.Re
 	// bdev scan 外层函数，内部通过 bdev 包下的 setupProvider 最终使用spdkbackend
 	h.setupProvider(log)
 
+	// helper app 收到请求，构建provider 调用scan
 	sRes, err := h.bdevProvider.Scan(sReq)
 	if err != nil {
 		return pbin.NewResponseWithError(err)
diff --git a/src/control/cmd/daos_server_helper/main.go b/src/control/cmd/daos_server_helper/main.go
index 6d118b54614..b0a7a6ce769 100644
--- a/src/control/cmd/daos_server_helper/main.go
+++ b/src/control/cmd/daos_server_helper/main.go
@@ -13,6 +13,7 @@ import (
 )
 
 func main() {
+	// daos_server 可以调用daos_server_helper
 	app := pbin.NewApp().
 		WithAllowedCallers("daos_server")
 
diff --git a/src/control/pbin/app.go b/src/control/pbin/app.go
index 7f43ca478d8..aa47e586d87 100644
--- a/src/control/pbin/app.go
+++ b/src/control/pbin/app.go
@@ -86,6 +86,7 @@ func (a *App) configureLogging(logPath string) {
 
 // WithAllowedCallers adds a list of process names allowed to call this
 // application.
+// 添加一个列表，允许调用当前app
 func (a *App) WithAllowedCallers(callers ...string) *App {
 	a.allowedCallers = callers
 	return a
@@ -123,7 +124,7 @@ func (a *App) logError(err error) error {
 }
 
 // Run executes the helper application process.
-
+// 执行helper app
 func (a *App) Run() error {
 	parentName, err := a.process.ParentProcessName()
 	if err != nil {
@@ -153,6 +154,7 @@ func (a *App) Run() error {
 		return a.logError(err)
 	}
 
+	// 处理请求
 	resp := a.handleRequest(req)
 
 	err = a.writeResponse(resp, conn)
@@ -206,6 +208,7 @@ func (a *App) readRequest(rdr io.Reader) (*Request, error) {
 }
 
 func (a *App) handleRequest(req *Request) *Response {
+	// 按照名字获取hdl
 	reqHandler, ok := a.handlers[req.Method]
 	if !ok {
 		err := a.logError(errors.Errorf("unhandled method %q", req.Method))
diff --git a/src/control/pbin/exec.go b/src/control/pbin/exec.go
index 7d2bf775c62..4e6b5707b10 100644
--- a/src/control/pbin/exec.go
+++ b/src/control/pbin/exec.go
@@ -122,6 +122,8 @@ func ReadMessage(conn io.Reader) ([]byte, error) {
 
 // ExecReq executes the supplied Request by starting a child process
 // to service the request. Returns a Response if successful.
+// 开启一个子协程执行转发命令
+// binPath 为 "daos_server_helper"
 func ExecReq(parent context.Context, log logging.Logger, binPath string, req *Request) (res *Response, err error) {
 	if req == nil {
 		return nil, errors.New("nil request")
@@ -130,6 +132,7 @@ func ExecReq(parent context.Context, log logging.Logger, binPath string, req *Re
 	ctx, killChild := context.WithCancel(parent)
 	defer killChild()
 
+	// 传入bin，调用go api
 	child := exec.CommandContext(ctx, binPath)
 	child.Stderr = &cmdLogger{
 		logFn:  log.Error,
@@ -160,12 +163,14 @@ func ExecReq(parent context.Context, log logging.Logger, binPath string, req *Re
 	defer func() {
 		// If there was an error, kill the child so that it can't
 		// hang around waiting for input.
+		// 出错时，主动kill child
 		if err != nil {
 			killChild()
 			return
 		}
 
 		// Otherwise, the child should exit normally.
+		// 成功时，child 会自动退出
 		err = child.Wait()
 	}()
 
diff --git a/src/control/pbin/forwarding.go b/src/control/pbin/forwarding.go
index 11e296d069a..dcfa193bc38 100644
--- a/src/control/pbin/forwarding.go
+++ b/src/control/pbin/forwarding.go
@@ -20,6 +20,7 @@ import (
 
 type (
 	// Forwarder provides a common implementation of a request forwarder.
+	// 提供通用的请求转发功能
 	Forwarder struct {
 		Disabled bool
 
@@ -57,6 +58,7 @@ func NewForwarder(log logging.Logger, pbinName string) *Forwarder {
 }
 
 // GetBinaryName returns the name of the binary requests will be forwarded to.
+// 获取请求要转发到的二进制程序名字，这里是转给daos_server_helper
 func (f *Forwarder) GetBinaryName() string {
 	return f.pbinName
 }
@@ -74,6 +76,7 @@ func (f *Forwarder) CanForward() bool {
 // SendReq is responsible for marshaling the forwarded request into a message
 // that is sent to the privileged binary, then unmarshaling the response for
 // the caller.
+// 负责转发给又特权的 daos_server_helper
 func (f *Forwarder) SendReq(method string, fwdReq interface{}, fwdRes interface{}) error {
 	if fwdReq == nil {
 		return errors.New("nil request")
@@ -82,6 +85,7 @@ func (f *Forwarder) SendReq(method string, fwdReq interface{}, fwdRes interface{
 		return errors.New("nil response")
 	}
 
+	// 找daos_server_helper
 	pbinPath, err := common.FindBinary(f.pbinName)
 	if err != nil {
 		return err
@@ -92,12 +96,15 @@ func (f *Forwarder) SendReq(method string, fwdReq interface{}, fwdRes interface{
 		return errors.Wrap(err, "failed to marshal forwarded request as payload")
 	}
 
+	// 构建req
 	req := &Request{
 		Method:  method,
 		Payload: payload,
 	}
 
 	ctx := context.TODO()
+	// 抓发执行cmd
+	// pbinPath 为daos_server_helper
 	res, err := ExecReq(ctx, f.log, pbinPath, req)
 	if err != nil {
 		if fault.IsFault(err) {
diff --git a/src/control/server/config/server.go b/src/control/server/config/server.go
index 42873a0da35..d5a1ec0e1b2 100644
--- a/src/control/server/config/server.go
+++ b/src/control/server/config/server.go
@@ -399,6 +399,7 @@ func (cfg *Server) SetPath(inPath string) error {
 	return err
 }
 
+// active 配置文件：/var/run/daos_server/.daos_server.active.yml
 // SaveActiveConfig saves read-only active config, tries config dir then /tmp/.
 func (cfg *Server) SaveActiveConfig(log logging.Logger) {
 	activeConfig := filepath.Join(cfg.SocketDir, ConfigOut)
@@ -650,10 +651,12 @@ func (cfg *Server) Validate(log logging.Logger) (err error) {
 	}
 
 	// Set DisableVMD reference if unset in config file.
+	// 如果配置中没有默认为 vmd 开启
 	if cfg.DisableVMD == nil {
 		cfg.WithDisableVMD(false)
 	}
 
+	// 日志中：vfio=true hotplug=false vmd=true requested in config
 	log.Debugf("vfio=%v hotplug=%v vmd=%v requested in config", !cfg.DisableVFIO,
 		cfg.EnableHotplug, !(*cfg.DisableVMD))
 
diff --git a/src/control/server/ctl_storage.go b/src/control/server/ctl_storage.go
index 9f2cef6ace5..40b09574634 100644
--- a/src/control/server/ctl_storage.go
+++ b/src/control/server/ctl_storage.go
@@ -25,6 +25,7 @@ import (
 // StorageControlService encapsulates the storage part of the control service
 type StorageControlService struct {
 	log             logging.Logger
+	// provider 包含多种类型的抽象类
 	storage         *storage.Provider
 	instanceStorage map[uint32]*storage.Config
 	getMemInfo      common.GetMemInfoFn
@@ -58,6 +59,7 @@ func (scs *StorageControlService) WithVMDEnabled() *StorageControlService {
 }
 
 // NewStorageControlService returns an initialized *StorageControlService
+// 构建最外层的service
 func NewStorageControlService(log logging.Logger, ecs []*engine.Config) *StorageControlService {
 	topCfg := &storage.Config{
 		Tiers: nil,
@@ -70,9 +72,11 @@ func NewStorageControlService(log logging.Logger, ecs []*engine.Config) *Storage
 		instanceStorage[uint32(i)] = &c.Storage
 	}
 
+	// 构建scs
 	return &StorageControlService{
 		log:             log,
 		instanceStorage: instanceStorage,
+		// 使用默认的provider
 		storage:         storage.DefaultProvider(log, 0, topCfg),
 		getMemInfo:      common.GetMemInfo,
 	}
diff --git a/src/control/server/ctl_svc.go b/src/control/server/ctl_svc.go
index bbe2741a4d8..5afe5bf11ab 100644
--- a/src/control/server/ctl_svc.go
+++ b/src/control/server/ctl_svc.go
@@ -16,6 +16,7 @@ import (
 
 // ControlService implements the control plane control service, satisfying
 // ctlpb.CtlSvcServer, and is the data container for the service.
+// 控制层服务
 type ControlService struct {
 	ctlpb.UnimplementedCtlSvcServer
 	StorageControlService
diff --git a/src/control/server/mgmt_svc.go b/src/control/server/mgmt_svc.go
index 5441f76d3a0..97d9dbbc759 100644
--- a/src/control/server/mgmt_svc.go
+++ b/src/control/server/mgmt_svc.go
@@ -66,6 +66,7 @@ func (br *batchRequest) sendResponse(parent context.Context, msg proto.Message,
 
 // mgmtSvc implements (the Go portion of) Management Service, satisfying
 // mgmtpb.MgmtSvcServer.
+// go 语言部分的管理服务
 type mgmtSvc struct {
 	mgmtpb.UnimplementedMgmtSvcServer
 	log               logging.Logger
diff --git a/src/control/server/server.go b/src/control/server/server.go
index 95803fed4b3..0e2427a3264 100644
--- a/src/control/server/server.go
+++ b/src/control/server/server.go
@@ -69,8 +69,10 @@ func processConfig(log logging.Logger, cfg *config.Server, fis *hardware.FabricI
 		}
 	}
 
+	// 保存active 配置文件：/var/run/daos_server/.daos_server.active.yml
 	cfg.SaveActiveConfig(log)
 
+	// 设置daos server helper 的env
 	if err := setDaosHelperEnvs(cfg, osSetenv); err != nil {
 		return err
 	}
@@ -195,11 +197,14 @@ func (srv *server) createServices(ctx context.Context) (err error) {
 	if err != nil {
 		return
 	}
+	// todo: mb
 	srv.membership = system.NewMembership(srv.log, srv.sysdb)
 
 	// Create rpcClient for inter-server communication.
+	// todo: 哪个rpc
 	cliCfg := control.DefaultConfig()
 	cliCfg.TransportConfig = srv.cfg.TransportConfig
+	// 客户端作用
 	rpcClient := control.NewClient(
 		control.WithClientComponent(build.ComponentServer),
 		control.WithConfig(cliCfg),
@@ -208,12 +213,14 @@ func (srv *server) createServices(ctx context.Context) (err error) {
 	// Create event distribution primitives.
 	srv.pubSub = events.NewPubSub(ctx, srv.log)
 	srv.OnShutdown(srv.pubSub.Close)
+	// todo: 事件转发
 	srv.evtForwarder = control.NewEventForwarder(rpcClient, srv.cfg.AccessPoints)
 	srv.evtLogger = control.NewEventLogger(srv.log)
 
-	// nvme 的控制器服务，prepare 和scan 请求都会通过这个控制器服务来完成
+	// 1. 控制层服务，prepare 和scan 请求都会通过这个控制器服务来完成
 	srv.ctlSvc = NewControlService(srv.log, srv.harness, srv.cfg, srv.pubSub,
 		hwprov.DefaultFabricScanner(srv.log))
+	// 2. 管理层服务
 	srv.mgmtSvc = newMgmtSvc(srv.harness, srv.membership, srv.sysdb, rpcClient, srv.pubSub)
 
 	if err := srv.mgmtSvc.systemProps.UpdateCompPropVal(daos.SystemPropertyDaosSystem, func() string {
@@ -336,6 +343,7 @@ func (srv *server) addEngines(ctx context.Context) error {
 
 	// Retrieve NVMe device details (before engines are started) so static details can be
 	// recovered by the engine storage provider(s) during scan even if devices are in use.
+	// 获取nvme 设备的详细信息
 	nvmeScanResp, err := scanBdevStorage(srv)
 	if err != nil {
 		return err
@@ -594,6 +602,7 @@ func Start(log logging.Logger, cfg *config.Server) error {
 		return errors.Wrapf(err, "retrieve system memory info")
 	}
 
+	// 处理配置文件
 	if err = processConfig(log, cfg, fis, mi, lookupIF, genFiAffFn(fis)); err != nil {
 		return err
 	}
@@ -604,6 +613,8 @@ func Start(log logging.Logger, cfg *config.Server) error {
 	if err != nil {
 		return err
 	}
+
+	// 日志：fault domain: /server01。配置文件中没配置，默认是host 级别
 	log.Debugf("fault domain: %s", faultDomain.String())
 
 	// 根据容错域和配置信息新建server
diff --git a/src/control/server/server_utils.go b/src/control/server/server_utils.go
index 98b7d3218fc..6f73668dac9 100644
--- a/src/control/server/server_utils.go
+++ b/src/control/server/server_utils.go
@@ -370,8 +370,10 @@ func prepBdevStorage(srv *server, iommuEnabled bool) error {
 }
 
 // scanBdevStorage performs discovery and validates existence of configured NVMe SSDs.
+// scan 操作用于发现和检查conf 中指定的nvme 是否存在
 func scanBdevStorage(srv *server) (*storage.BdevScanResponse, error) {
-	// 执行dmg storage scan 时会打印
+	// 1. 执行dmg storage scan 时会打印
+	// 2. server 启动时候自动会去scan，也会打印，from func addEngines
 	defer srv.logDuration(track("time to scan bdev storage"))
 
 	if srv.cfg.DisableHugepages {
@@ -379,6 +381,7 @@ func scanBdevStorage(srv *server) (*storage.BdevScanResponse, error) {
 		return &storage.BdevScanResponse{}, nil
 	}
 
+	// 执行scan
 	nvmeScanResp, err := srv.ctlSvc.NvmeScan(storage.BdevScanRequest{
 		DeviceList: getBdevCfgsFromSrvCfg(srv.cfg).Bdevs(),
 	})
diff --git a/src/control/server/storage/bdev.go b/src/control/server/storage/bdev.go
index 47252668ea5..b05d153140f 100644
--- a/src/control/server/storage/bdev.go
+++ b/src/control/server/storage/bdev.go
@@ -689,6 +689,7 @@ type BdevForwarder struct {
 	NVMeFirmwareForwarder
 }
 
+// admin 转发器
 func NewBdevForwarder(log logging.Logger) *BdevForwarder {
 	return &BdevForwarder{
 		BdevAdminForwarder:    *NewBdevAdminForwarder(log),
@@ -701,7 +702,9 @@ type BdevAdminForwarder struct {
 	reqMutex sync.Mutex
 }
 
+// admin转发器
 func NewBdevAdminForwarder(log logging.Logger) *BdevAdminForwarder {
+	// "daos_server_helper"
 	pf := pbin.NewForwarder(log, pbin.DaosPrivHelperName)
 
 	return &BdevAdminForwarder{
@@ -720,6 +723,7 @@ func (f *BdevAdminForwarder) Scan(req BdevScanRequest) (*BdevScanResponse, error
 	req.Forwarded = true
 
 	res := new(BdevScanResponse)
+	// 发送bdevscan 命令给daos_admin(daos_server_helper)
 	if err := f.SendReq("BdevScan", req, res); err != nil {
 		return nil, err
 	}
diff --git a/src/control/server/storage/bdev/backend.go b/src/control/server/storage/bdev/backend.go
index 68df11e093c..031f3c9f5ad 100644
--- a/src/control/server/storage/bdev/backend.go
+++ b/src/control/server/storage/bdev/backend.go
@@ -356,6 +356,13 @@ func groomDiscoveredBdevs(reqDevs *hardware.PCIAddressSet, discovered storage.Nv
 
 // Scan discovers NVMe controllers accessible by SPDK.
 // scan 将发现nvme controller
+// 这行日志在daos_admin.log 中打印
+// todo: 这里vmd enable 为啥变成false 了
+/*
+root@server01:~# cat /tmp/daos_admin.log | grep 'spdk backend scan'
+DEBUG 10:54:22.167713 backend.go:330: spdk backend scan (bindings discover call): {ForwardableRequest:{Forwarded:true} DeviceList:0000:65:00.0,0000:66:00.0,0000:67:00.0,0000:68:00.0,0000:e3:00.0,0000:e4:00.0,0000:e5:00.0,0000:e6:00.0 VMDEnabled:false BypassCache:false}
+DEBUG 09:21:10.103772 backend.go:330: spdk backend scan (bindings discover call): {ForwardableRequest:{Forwarded:true} DeviceList:0000:65:00.0,0000:66:00.0,0000:67:00.0,0000:68:00.0,0000:e3:00.0,0000:e4:00.0,0000:e5:00.0,0000:e6:00.0 VMDEnabled:false BypassCache:false}
+*/
 func (sb *spdkBackend) Scan(req storage.BdevScanRequest) (*storage.BdevScanResponse, error) {
 	sb.log.Debugf("spdk backend scan (bindings discover call): %+v", req)
 
diff --git a/src/control/server/storage/bdev/provider.go b/src/control/server/storage/bdev/provider.go
index e747100f4b7..d980eda4b20 100644
--- a/src/control/server/storage/bdev/provider.go
+++ b/src/control/server/storage/bdev/provider.go
@@ -56,8 +56,12 @@ func NewProvider(log logging.Logger, backend Backend) *Provider {
 
 // Scan calls into the backend to discover NVMe components in the
 // system.
+// backend 是spdkWrapper
 func (p *Provider) Scan(req storage.BdevScanRequest) (resp *storage.BdevScanResponse, err error) {
 	p.log.Debug("run bdev storage provider scan")
+	// func (sb *spdkBackend) Scan(
+	// defaultBackend 就是backend
+	// func (sb *spdkBackend) Scan(req storage.BdevScanRequest) (
 	return p.backend.Scan(req)
 }
 
diff --git a/src/control/server/storage/provider.go b/src/control/server/storage/provider.go
index fae9e88506e..c39483d4eee 100644
--- a/src/control/server/storage/provider.go
+++ b/src/control/server/storage/provider.go
@@ -51,6 +51,9 @@ func DefaultProvider(log logging.Logger, idx int, engineStorage *Config) *Provid
 	if engineStorage == nil {
 		engineStorage = new(Config)
 	}
+
+	// 参数6 为转发器
+	// func NewProvider(log logging.Logger, idx int, engineStorage *Config, sys SystemProvider, scm ScmProvider, bdev BdevProvider, meta MetadataProvider)
 	return NewProvider(log, idx, engineStorage, system.DefaultProvider(),
 		NewScmForwarder(log), NewBdevForwarder(log), NewMetadataForwarder(log))
 }
@@ -732,12 +735,15 @@ func (p *Provider) ScanBdevTiers(direct bool) (results []BdevTierScanResult, err
 
 // ScanBdevs calls into bdev storage provider to scan SSDs, always bypassing cache.
 // Function should not be called when engines have been started and SSDs have been claimed by SPDK.
+// 类似c++多态，不同的provider 执行不同的scan 函数
 func (p *Provider) ScanBdevs(req BdevScanRequest) (*BdevScanResponse, error) {
 	p.RLock()
 	defer p.RUnlock()
 
+	// vmd 默认是enable
 	req.VMDEnabled = p.vmdEnabled
-	// func (p *Provider) Scan(
+	// func (p *Provider) Scan(  --> func (sb *spdkBackend) Scan(req storage.BdevScanRequest) (
+	// 开始scan，具体bdev 是不是NewBdevForwarder，就要看provider 的类型了，类似多态的效果
 	return p.bdev.Scan(req)
 }
 
@@ -803,6 +809,7 @@ func NewProvider(log logging.Logger, idx int, engineStorage *Config, sys SystemP
 		engineStorage: engineStorage,
 		Sys:           sys,
 		scm:           scm,
+		// NewBdevForwarder 转发器
 		bdev:          bdev,
 		metadata:      meta,
 	}
diff --git a/src/engine/init.c b/src/engine/init.c
index 183c9c1c6d5..dca6d12c0d0 100644
--- a/src/engine/init.c
+++ b/src/engine/init.c
@@ -839,6 +839,34 @@ metrics_region_size(int num_tgts)
 	return (est_std_metrics + est_tgt_metrics * num_tgts) * D_TM_METRIC_SIZE;
 }
 
+// daos 的libbio.so 依赖的部分spdk 模块
+// 1. spdk_bdev
+// 2. spdk_bdev_nvme
+// 3. spdk_nvme
+// 4. spdk_vmd
+// 5. spdk_event_bdev
+/*
+daos 等bdev 创建命令是daos_xxx_create，而nvme 类型创建命令是：bdev_nvme_attach_controller
+p = subparsers.add_parser('bdev_nvme_attach_controller', aliases=['construct_nvme_bdev']
+root@server02:/opt/daos/prereq/release/spdk/lib# ldd libspdk_bdev.so
+        linux-vdso.so.1 (0x00007ffeb66ab000)
+        libspdk_log.so.4.1 => /opt/daos/prereq/release/spdk/lib/libspdk_log.so.4.1 (0x00007fb6bcfb9000)
+        libspdk_util.so.4.1 => /opt/daos/prereq/release/spdk/lib/libspdk_util.so.4.1 (0x00007fb6bcfa6000)
+        libspdk_thread.so.6.1 => /opt/daos/prereq/release/spdk/lib/libspdk_thread.so.6.1 (0x00007fb6bcf97000)
+        libspdk_json.so.3.3 => /opt/daos/prereq/release/spdk/lib/libspdk_json.so.3.3 (0x00007fb6bcf8b000)
+        libspdk_jsonrpc.so.3.0 => /opt/daos/prereq/release/spdk/lib/libspdk_jsonrpc.so.3.0 (0x00007fb6bcf81000)
+        libspdk_rpc.so.3.0 => /opt/daos/prereq/release/spdk/lib/libspdk_rpc.so.3.0 (0x00007fb6bcf78000)
+        libspdk_notify.so.3.0 => /opt/daos/prereq/release/spdk/lib/libspdk_notify.so.3.0 (0x00007fb6bcf32000)
+        libspdk_trace.so.5.1 => /opt/daos/prereq/release/spdk/lib/libspdk_trace.so.5.1 (0x00007fb6bcf29000)
+        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fb6bcd22000)
+        libuuid.so.1 => /lib/x86_64-linux-gnu/libuuid.so.1 (0x00007fb6bcd19000)
+        libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fb6bcbca000)
+        /lib64/ld-linux-x86-64.so.2 (0x00007fb6bcfe1000)
+        libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007fb6bcba3000)
+        librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007fb6bcb99000)
+        libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fb6bcb76000)
+
+*/
 static int
 server_init(int argc, char *argv[])
 {
diff --git a/src/vos/SConscript b/src/vos/SConscript
index 36e71260ec1..b819f26252e 100644
--- a/src/vos/SConscript
+++ b/src/vos/SConscript
@@ -31,6 +31,7 @@ def build_vos(env, standalone):
     denv.Install('$PREFIX/lib64/daos_srv', vos)
 
 
+# libvos_size.so 依赖libbio.so
 def build_vos_internal(env):
     """build vos internal"""
     denv = env.Clone()