Vraid essentially, it spreads every LUN over every disk in the EVA. ( Best practice is to configure all physical disks in an EVA in a single group.)
Raid is manually or semi-wizard-assisted, that select physical disks make up the raid-set.
Vraid is a term used for virtual raid arrays, in HP world they come in Vraid 0 Vraid 1 or Vraid 5 flavours, no other Vraid exist, in an 8 disk array a normal raid array of raid 5 would require at least 3 disk, in the EVA Vraid 5 all 8 disks would be used but the load spread virtually and even over all the 8 disks, this means higher effiiciency and less failure (allegedly), you could also have a raid 1 with 2 extra disks so you have used up min 5 of you 8 normal raid disk, you can havea Vraid 1 and still be using all the space on the 8 disks, in which case data is striped more in line wtih a Raid 1+0 than a Raid 1 but its HP terminology.
basically its virtualised storage which offers better performance and higher efficiency than standard raid with better protection levels. (HP disk gorups have more levels of protectin than standard Raid sets)
hope this helps