Storage server was down

Hi

how can we solve the below issue.

Info nbjm(pid=6684) starting backup job (jobid=725524) for client XXXXXX, policy LP_Unix, schedule Full  

4/6/2014 12:32:53 PM - Info nbjm(pid=6684) requesting STANDARD_RESOURCE resources from RB for backup job (jobid=725524, request id:{D6B8CAEE-733E-4D90-8A34-9933FB91123A})  
4/6/2014 12:32:53 PM - requesting resource lpmedia1-dxi2500
4/6/2014 12:32:53 PM - requesting resource pwnbu1.NBU_CLIENT.MAXJOBS.lpavpms01
4/6/2014 12:32:53 PM - requesting resource pwnbu1.NBU_POLICY.MAXJOBS.LP_Unix
4/6/2014 12:32:53 PM - Error nbjm(pid=6684) NBU status: 2106, EMM status: Storage Server is down or unavailable  
Disk storage server is down(2106)