The "PVHVM" image appears to have disappeared from RAX, replaced with
a "Cloud" image.
Maybe I haven't looked in the right place, but I can't find any info
on if, why or when this was updated. But I started a server with the
"Cloud" image and it seems the same as the PVHVM image to me; hdparm
showed read speads the same as a older server and dd writes to a file
were the same speed (recorded below for posterity).
ianw@nb04:~$ dd if=/dev/zero of=testfile bs=1G count=1 oflag=direct
1+0 records in
1+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 5.21766 s, 206 MB/s
ianw@nb04:~$ sudo hdparm -Tt /dev/xvda
Timing cached reads: 16428 MB in 1.99 seconds = 8263.05 MB/sec
Timing buffered disk reads: 752 MB in 3.00 seconds = 250.65 MB/sec
From looking at dmesg it has
[ 0.000000] DMI: Xen HVM domU, BIOS 4.1.5 11/28/2013
[ 0.000000] Hypervisor detected: Xen HVM
[ 0.000000] Xen version 4.1.
[ 0.000000] Xen Platform PCI: I/O protocol version 1
[ 0.000000] Netfront and the Xen platform PCI driver have been compiled for this kernel: unplug emulated NICs.
[ 0.000000] Blkfront and the Xen platform PCI driver have been compiled for this kernel: unplug emulated disks.
which, if  is anything to go by suggests it is in PVHVM mode
tl;dr seems like the image name changed.