You haven't mentioned if this is Virtual array or Linear array. I am assuming this is Linear array.
If you have ESX VM then you can migrate your VMs to some other Storage with the help of Vmotion feature of ESX. Then delete the vdisk and volumes to existing drives and replace them with new drives. Then recreate vdisk and volumes. Then migrate back your VMs from other Storage to MSA again
Other option I could think of take data backup, delete existing vdisk/volumes of the MSA. Then replace with 4TB drives and then create new vdisk/volumes. Then restaore data from backup
Another option could be very much time consuming. You can replace one 2TB drive with one 4TB drive and wait for reconstruction to get completed. Then go for next drive replacement. I am assuming they are in RAID 5 or RAID 6. Once all 10 drives replaced with all 4TB drives then you need to take data backup and then go for vdisk expansion with 2 drives.
Hope this helps!
Regards
Subhajit
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