I have one Vmware Server 1 on Windows host OS. I guess you use vmware server 2 on Linux host OS. For that reason I offer you two possible options.
1. If full disk that you have is mounted in /var/lib/vmware/Virtual Machines without LVM support you need to mount new disk on the other place and to store VM files on the new place. This of course will involve with downtime of the VMs. If you use this variant part of the machines will be on the old hisk, part of them on the new one.
2. If full disk that you have is mounted in /var/lib/vmware/Virtual Machines with LVM support you can add new disk to LVM and now you have on /var/lib/vmware/Virtual Machines additional free space equal to the amount of new hard disk.
Both options are very insecure, because if one disk fail you will lose all information on them if use variant 2 or will lose all information on the damaged disc if use variant 1.