diff --git a/src/cryptobox/core/blockdevice.py b/src/cryptobox/core/blockdevice.py
index 13abc4e..8536520 100644
--- a/src/cryptobox/core/blockdevice.py
+++ b/src/cryptobox/core/blockdevice.py
@@ -51,7 +51,7 @@ MAJOR_DEVNUM_MD_RAID = 9
 
 ## cache settings
 CACHE_ENABLED = True
-CACHE_EXPIRE_SECONDS = 60
+CACHE_EXPIRE_SECONDS = 120
 CACHE_MONITOR_FILE = '/proc/partitions'
 
 ## useful for manual profiling
@@ -139,7 +139,8 @@ class Blockdevice:
         @type empty_cache: boolean
         @param empty_cache: Whether to discard the cached information or not.
         """
-        CACHE.reset(["blockdevice_info", self.name])
+        if empty_cache:
+            CACHE.reset(["blockdevice_info", self.name])
         self.devnum = self.__get_major_minor()
         self.size = self.__get_size()
         self.size_human = self.__get_size_human()
@@ -387,8 +388,9 @@ class Blockdevice:
         """
         default = 0
         try:
-            size_kb = int(file(os.path.join(self.devdir, 'size')).read())
-            return int(size_kb/1024)
+            size_blocks = int(file(os.path.join(self.devdir, 'size')).read())
+            ## size is defined as the number of blocks (512 byte)
+            return int(size_blocks/512)
         except OSError:
             return default
         except ValueError: