As the others have already said, using existing raid groups for new LUNs is possible, but you should know what your existing workload is and what the new workload will be. Is the current load random IO, mostly Writes, large block? Is the new workload small block sequential Writes?  You need to know the workloads to determine is the existing raid groups can handle the new workload. See the EMC Best Practices guide for CX3 (I've attached a copy). See the section called "Sizing the Storage System" near the end of the doc.  glen
We have a CX3-10c with 7 VMware ESX 3.5 U5 hosts. We are considering moving two of our hosts to Hyper-V-based servers. We currently have 8 RAID groups defined on the CX3-10c. All of the RAID groups contain at least a few LUNs formatted with VMFS. Will it cause any problems if we create new LUNs from unused RAID group space formatted for use by Hyper-V? In other words, will having VMFS and NTFS LUNs in the same RAID group cause any problems? Or, does the SAN and hosts not care? As part of this change we are planning to create a new Storage Group and only expose the NTFS LUNs to the Hyper-V hosts.  Thoughts?  Thanks, Jay
Hyper-V and VMware using same RAID group in CX3-10c