If you didn't specify particular version of sql server for HPC
then default installation is the Sql Server 2008 express or R2
In my case, we have a HPC Server 2008 R2 with SQL Server 2008 express r2 as default installation.
SQL Sever express R2 does not support big storage like over 10GB.
You can refer site here. http://www.microsoft.com/express/Database/
My suggestion is
1. Go to HPC 2008 R2 Cluster Manager
2. Select Configuration section
3. Select "Configure job scheduler policies and settings" on Deployment to-do List
4. Change number of days of "Job record retention period" that
determine how many days of completed jobs you wish to keep
I think it would help you to avoid your problem if you have limited tasks of jobs which SQL Sever Express can cover.
I hope it can help you.
Thank You
DongYong