diff --git a/src/NzbDrone.Core/DiskSpace/DiskSpaceService.cs b/src/NzbDrone.Core/DiskSpace/DiskSpaceService.cs
index c9846b084..7b3950347 100644
--- a/src/NzbDrone.Core/DiskSpace/DiskSpaceService.cs
+++ b/src/NzbDrone.Core/DiskSpace/DiskSpaceService.cs
@@ -6,6 +6,7 @@ using System.Text.RegularExpressions;
 using NLog;
 using NzbDrone.Common.Disk;
 using NzbDrone.Common.Extensions;
+using NzbDrone.Core.RootFolders;
 using NzbDrone.Core.Tv;
 
 namespace NzbDrone.Core.DiskSpace
@@ -18,14 +19,16 @@ namespace NzbDrone.Core.DiskSpace
     public class DiskSpaceService : IDiskSpaceService
     {
         private readonly ISeriesService _seriesService;
+        private readonly IRootFolderService _rootFolderService;
         private readonly IDiskProvider _diskProvider;
         private readonly Logger _logger;
 
         private static readonly Regex _regexSpecialDrive = new Regex("^/var/lib/(docker|rancher|kubelet)(/|$)|^/(boot|etc)(/|$)|/docker(/var)?/aufs(/|$)", RegexOptions.Compiled);
 
-        public DiskSpaceService(ISeriesService seriesService, IDiskProvider diskProvider, Logger logger)
+        public DiskSpaceService(ISeriesService seriesService, IRootFolderService rootFolderService, IDiskProvider diskProvider, Logger logger)
         {
             _seriesService = seriesService;
+            _rootFolderService = rootFolderService;
             _diskProvider = diskProvider;
             _logger = logger;
         }
@@ -43,9 +46,15 @@ namespace NzbDrone.Core.DiskSpace
 
         private IEnumerable<string> GetSeriesRootPaths()
         {
+            // Get all series paths and find the correct root folder for each. For each unique root folder path,
+            // ensure the path exists and get its path root and return all unique path roots.
+
             return _seriesService.GetAllSeriesPaths()
-                .Where(s => s.Value.IsPathValid(PathValidationType.CurrentOs) && _diskProvider.FolderExists(s.Value))
-                .Select(s => _diskProvider.GetPathRoot(s.Value))
+                .Where(s => s.Value.IsPathValid(PathValidationType.CurrentOs))
+                .Select(s => _rootFolderService.GetBestRootFolderPath(s.Value))
+                .Distinct()
+                .Where(r => _diskProvider.FolderExists(r))
+                .Select(r => _diskProvider.GetPathRoot(r))
                 .Distinct();
         }
 
diff --git a/src/NzbDrone.Core/RootFolders/RootFolderService.cs b/src/NzbDrone.Core/RootFolders/RootFolderService.cs
index da039e967..cd3d1c835 100644
--- a/src/NzbDrone.Core/RootFolders/RootFolderService.cs
+++ b/src/NzbDrone.Core/RootFolders/RootFolderService.cs
@@ -5,6 +5,7 @@ using System.Linq;
 using System.Threading.Tasks;
 using NLog;
 using NzbDrone.Common;
+using NzbDrone.Common.Cache;
 using NzbDrone.Common.Disk;
 using NzbDrone.Common.Extensions;
 using NzbDrone.Core.Organizer;
@@ -30,6 +31,8 @@ namespace NzbDrone.Core.RootFolders
         private readonly INamingConfigService _namingConfigService;
         private readonly Logger _logger;
 
+        private readonly ICached<string> _cache;
+
         private static readonly HashSet<string> SpecialFolders = new HashSet<string>
                                                                  {
                                                                      "$recycle.bin",
@@ -47,6 +50,7 @@ namespace NzbDrone.Core.RootFolders
                                  IDiskProvider diskProvider,
                                  ISeriesRepository seriesRepository,
                                  INamingConfigService namingConfigService,
+                                 ICacheManager cacheManager,
                                  Logger logger)
         {
             _rootFolderRepository = rootFolderRepository;
@@ -54,6 +58,8 @@ namespace NzbDrone.Core.RootFolders
             _seriesRepository = seriesRepository;
             _namingConfigService = namingConfigService;
             _logger = logger;
+
+            _cache = cacheManager.GetCache<string>(GetType());
         }
 
         public List<RootFolder> All()
@@ -110,19 +116,21 @@ namespace NzbDrone.Core.RootFolders
 
             if (!_diskProvider.FolderWritable(rootFolder.Path))
             {
-                throw new UnauthorizedAccessException(string.Format("Root folder path '{0}' is not writable by user '{1}'", rootFolder.Path, Environment.UserName));
+                throw new UnauthorizedAccessException($"Root folder path '{rootFolder.Path}' is not writable by user '{Environment.UserName}'");
             }
 
             _rootFolderRepository.Insert(rootFolder);
             var seriesPaths = _seriesRepository.AllSeriesPaths();
 
             GetDetails(rootFolder, seriesPaths, true);
+            _cache.Clear();
 
             return rootFolder;
         }
 
         public void Remove(int id)
         {
+            _cache.Clear();
             _rootFolderRepository.Delete(id);
         }
 
@@ -186,16 +194,7 @@ namespace NzbDrone.Core.RootFolders
 
         public string GetBestRootFolderPath(string path)
         {
-            var possibleRootFolder = All().Where(r => r.Path.IsParentPath(path)).MaxBy(r => r.Path.Length);
-
-            if (possibleRootFolder == null)
-            {
-                var osPath = new OsPath(path);
-
-                return osPath.Directory.ToString().TrimEnd(osPath.IsUnixPath ? '/' : '\\');
-            }
-
-            return possibleRootFolder?.Path;
+            return _cache.Get(path, () => GetBestRootFolderPathInternal(path), TimeSpan.FromDays(1));
         }
 
         private void GetDetails(RootFolder rootFolder, Dictionary<int, string> seriesPaths, bool timeout)
@@ -211,5 +210,19 @@ namespace NzbDrone.Core.RootFolders
                 }
             }).Wait(timeout ? 5000 : -1);
         }
+
+        private string GetBestRootFolderPathInternal(string path)
+        {
+            var possibleRootFolder = All().Where(r => r.Path.IsParentPath(path)).MaxBy(r => r.Path.Length);
+
+            if (possibleRootFolder == null)
+            {
+                var osPath = new OsPath(path);
+
+                return osPath.Directory.ToString().TrimEnd(osPath.IsUnixPath ? '/' : '\\');
+            }
+
+            return possibleRootFolder.Path;
+        }
     }
 }