According to the Support Matrix:
Virtual disk size can exceed 2TB and is limited by the type of RAID group, number of drives in the RAID group and the size of the drives (Up to 45 disks can be used in RAID 0 and 44 disks in RAID 10. RAID 5 and RAID 6 are limited to a maximum of 30 disks)
http://support.dell.com/support/edocs/systems/md3000/en/supmatrx/Sup_Matx.pdf

For troubleshooting:
For information about troubleshooting MD3000 and MD3000i storage arrays,
refer to the “Troubleshooting Problems” chapter of the Dell™ PowerVault™
Modular Disk Storage Manager User’s Guide

Also, this may be of use:
dell.com/PowerVault POWERVAULTMD3000 AND MD3000i Array Tuning and Best practices
http://support.dell.com/support/edocs/systems/md3000/en/ts/MD3XarraytuningA01.pdf