var/cache/ will not populate

Question

I was taking a look through the var/cache/ folder to see what was contained there and noticed that the following folders were listed, but most of them were empty:

 mage--0
 mage--1
 mage--2
 mage--3
 mage--4
 mage--5
 mage--6
 mage--7
 mage--8
 mage--9
 mage--a
 mage--b
 mage--c
 mage--d
 mage--e
 mage--f

The only files in this cache set was the following:

 var/cache/mage--4/mage---e54_CORE_CACHE_OPTIONS
 var/cache/mage--4/mage---internal-metadatas---e54_CORE_CACHE_OPTIONS
 var/cache/mage--5/mage---e54_CORE_CACHE_INVALIDATE
 var/cache/mage--5/mage---internal-metadatas---e54_CORE_CACHE_INVALIDATE

Magento Install Info:

 Magento Version: CE 1.9.1.0
 OS: Amazon Linux AMI
 PHP 5.3.29
 MySQL 5.5.40
 Running Magento in a Multi-Store setup
 Not Running Redis or Memcache
 Not Running APC, Xcache, eAccelerator

Is this normal? I would assume that the every folder should have something in it other than just 4 files for the whole Magento install.

Could this be some sort of permissions problem with the var/cache folder?

UPDATE

adding the following into app/etc/local.xml inside the tags populated the var/cache folder with cache items

 <cache>
 <backend></backend>
 </cache>

Answer 1

Adding the following into app/etc/local.xml inside the tags populated the var/cache folder with cache items. Appears that this needed to be explicitly set which is a change from previous versions of Magento

 <cache>
 <backend></backend>
 </cache>