Lol, I'm seeing 10 users here. And based on lettering, I'd say there's 12-14 users. These are french servers, which means they're from OVH. And this specific server has 2 x 2TB drives.
That means, if he has not upgraded the number of drives (which I am sure he hasn't) then there's about 6-7 users sharing one physical drive. That's serious overselling and these are standard SATA2 drives; lots of rape which is why you're seeing slow as fuck rar/unrar.
Unless the OP can confirm that not more than 4-5 users (still a lot) are sharing one physical drive, then this is just a very bad purchase because you'll see this kind of sluggish performance all the time. SATA2 drives are not designed to be raped by so many people at the same time.