volume server:set the default value of "hasSlowRead" to true (#3710)

* simplify a bit

* feat: volume: add "readBufSize" option to customize read optimization

* refactor : redbufSIze -> readBufferSize

* simplify a bit

* simplify a bit

* volume server:set the default value of "hasSlowRead" to true

weed/command/volume.go

@@ -98,7 +98,7 @@ func init() {
 	v.metricsHttpPort = cmdVolume.Flag.Int("metricsPort", 0, "Prometheus metrics listen port")
 	v.idxFolder = cmdVolume.Flag.String("dir.idx", "", "directory to store .idx files")
 	v.inflightUploadDataTimeout = cmdVolume.Flag.Duration("inflightUploadDataTimeout", 60*time.Second, "inflight upload data wait timeout of volume servers")
-	v.hasSlowRead = cmdVolume.Flag.Bool("hasSlowRead", false, "<experimental> if true, this prevents slow reads from blocking other requests, but large file read P99 latency will increase.")
+	v.hasSlowRead = cmdVolume.Flag.Bool("hasSlowRead", true, "<experimental> if true, this prevents slow reads from blocking other requests, but large file read P99 latency will increase.")
 	v.readBufferSizeMB = cmdVolume.Flag.Int("readBufferSizeMB", 4, "<experimental> larger values can optimize query performance but will increase some memory usage,Use with hasSlowRead normally.")
 }