We are using IS 6.1 connected to Broker 6.1 on AIX. In one of our test environments the Utilization stats under broker admin show the reserved space equal to the max space. Used space for the broker is <1 %. We do not have this broker as part of any territories and have no documents in any client queues that I see. I am trying to determine what is making up the servered space and if this is causing problems for us. Other than see how to set reserved space upon startup I see very little documentation on this setting. I do see a few thread saying I need to add more storage files when this happens. I guess I would like to understand why. Anyone else see this before?

Found this in Advantage site thought it might be of some help for you

possible due to the mechanism that Broker uses to store documents in its storage.
Lets assume that we are dealing with a newly configured Broker, with no documents yet published to it.
As documents are published to Broker, Broker creates two types of storage regions: ‘Small’ and ‘Normal’ depending on what is required to store the size of document just published. The key point in Broker storage allocation is that it looks for contiguous blocks of storage space when allocating disk space for storage. Broker creates storage regions dynamically to meet allocation requests. In other words, Broker does not divide its storage into small and normal regions at startup, rather, it creates them on an as-needed basis.
As you keep publishing different sizes of documents to Broker, Broker keeps creating these regions, which then becomes/depicts the file storage pattern/regions for Broker. This does mean that the number of ‘small’ and ‘large’ regions created depend entirely on the size of documents published to Broker until the whole Broker storage pattern is laid out (Reserved Size = 100%).Once a region is created, its size cannot be altered. So in other words, if your publishing pattern has created 20 small regions and 8 normal regions in the capacity available, that will become the underlying storage pattern for your Broker.
“Lets assume that your publishing pattern has created a lot of small regions and not so many normal regions. When publishing, if all the small regions are full, another small document published can be stored in one of the normal regions. On the other hand, when a large document is published and if there is no space available in the normal regions or not enough contiguous space available to create a new normal region, Broker will not try to string together the small blocks/regions to store the large document.”
This is the situation when Broker will flag the out-of-storage exception although the storage used might show as only 50% used