diff --git a/dbms/src/Common/DiskSpaceMonitor.cpp b/dbms/src/Common/DiskSpaceMonitor.cpp
index bfcb396c52f..a7b6ccbcf28 100644
--- a/dbms/src/Common/DiskSpaceMonitor.cpp
+++ b/dbms/src/Common/DiskSpaceMonitor.cpp
@@ -231,19 +231,6 @@ const DiskPtr & DiskSelector::operator[](const String & name) const
 }
 
 
-bool DiskSelector::hasDisk(const String & name) const
-{
-    auto it = disks.find(name);
-    return it != disks.end();
-}
-
-
-void DiskSelector::add(const DiskPtr & disk)
-{
-    disks.emplace(disk->getName(), disk);
-}
-
-
 Volume::Volume(
     String name_,
     const Poco::Util::AbstractConfiguration & config,
@@ -523,6 +510,7 @@ StoragePolicySelector::StoragePolicySelector(
     constexpr auto default_volume_name = "default";
     constexpr auto default_disk_name = "default";
 
+    /// Add default if it's not specified explicetly
     if (policies.find(default_storage_policy_name) == policies.end())
     {
         auto default_volume = std::make_shared<Volume>(
diff --git a/dbms/src/Common/DiskSpaceMonitor.h b/dbms/src/Common/DiskSpaceMonitor.h
index e62ebe69d6a..0cd17f7e078 100644
--- a/dbms/src/Common/DiskSpaceMonitor.h
+++ b/dbms/src/Common/DiskSpaceMonitor.h
@@ -193,10 +193,6 @@ public:
 
     const DiskPtr & operator[](const String & name) const;
 
-    bool hasDisk(const String & name) const;
-
-    void add(const DiskPtr & disk);
-
     const auto & getDisksMap() const { return disks; }
 
 private:
@@ -262,6 +258,9 @@ public:
     /// Returns disks ordered by volumes priority
     Disks getDisks() const;
 
+    /// Returns any disk
+    /// Used when it's not important, for example for
+    /// mutations files
     DiskPtr getAnyDisk() const;
 
     DiskPtr getDiskByName(const String & disk_name) const;
@@ -311,7 +310,7 @@ private:
 using StoragePolicyPtr = std::shared_ptr<const StoragePolicy>;
 
 /// Parse .xml configuration and store information about policies
-/// Mostly used for introspection
+/// Mostly used for introspection.
 class StoragePolicySelector
 {
 public: