When I set up Samba I also set up a Samba user account so I can authenticate access for shares on my server. I set the account to the same as my local user account on my server so there wouldn't be any issues. I would say try and make the owner and group to your local account with chmod and see what happens, or try and add a Samba account.
It might also be important to note that you may have mounted the share with root. sudo mount /dev/sda3 /media/Raid5, or however you mounted the device since you use sudo it will mount the device with root permissions. You might be able to change the mount on fstab to look like:
That will allow any user to mount the device.
#Raid5 mount on /media/Raid5
/dev/sda3 /media/Raid5 ext4 rw,user,exec,dev,suid,async 0 0
To change the owner and group of a file, type (Change chris to your username):
You will need to changed the security under Authentication in smb.conf to security=user, you might just have to uncomment the line.
sudo chown chris.chris /media/Raid5
To add a Samba user, type:
Then under the share you defined in smb.conf, add "valid users = chris" Which will allow only chris to have access to that share.
sudo smbpasswd -a chris
Hope this helps