Hey, @Hornet, Excelsior and Liara helped me with that too,
Run this command it will help you to know how far your HDD is in the grave.
dd if=/dev/zero of=$HOME/test.img bs=1G count=1 oflag=direct
It should return you something like that
1+0 records in
1+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 137.002 s, 7.8 MB/s
It's your HDD transfert speed, a normal HDD goes around 100 MB/s (ie 119 on mine)
To approch Assitance, call them or create a ticket, telling that your server is anormally slow and include your test.
They probably purpose you an XC2015 at a reduced price as they did for both of us.
Hope it'll help you