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>