KVM SSD speed problem


I subscribed to a VPS where the storage supposed to be 100% SSD.
When I execute the following commands the result and performance are under my expectations (no any service is running on the VPS):
"stock@vmi87606:~/installation$ sudo smartctl -a /dev/sda
smartctl 6.5 2016-01-24 r4214 [x86_64-linux-4.4.0-42-generic] (local build)
Copyright © 2002-16, Bruce Allen, Christian Franke, www.smartmontools.org

Vendor: QEMU
Revision: 2.4.
User Capacity: 322,122,547,200 bytes [322 GB]
Logical block size: 512 bytes
LU is thin provisioned, LBPRZ=0
Rotation Rate: 5400 rpm
Device type: disk
Local Time is: Tue Oct 11 15:05:26 2016 CEST
SMART support is: Unavailable - device lacks SMART capability.

stock@vmi87606:~/installation$ dd if=/dev/zero of=test bs=1G count=1 oflag=direct
1+0 records in
1+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 11.1125 s, 96.6 MB/s

stock@vmi87606:~$ w
18:08:22 up 3:18, 3 users, load average: 0.14, 0.04, 0.01
stock tty7 :0 14:49 3:18m 47.35s 0.14s /sbin/upstart —user
stock pts/11 18:00 0.00s 0.01s 0.01s w
stock pts/1 :0.0 17:44 2:30 0.23s 0.23s bash

Why is it claim 5400RPM HDD and the speed of it below 100MB/s!?
The service operator claims: I’m the only one using the SSD, but I based on the output I doubt it…

Output from operator:

Your VPS is hosted on a host system with only SSD storage as you ordered it. Due
to the virtualization of your VPS it looks like you are only using harddisk
storage, but it is purely hosted on SSD. And a speedtest of your storage does
neither confirm that is a HDD nor that is a SSD as it depends on the usage of the
filesystem on the host system.



I’m not sure whether smartmontools can accurately identify qemu disks. Where the speed should be higher than what you get… I’m not sure!

I have tried on a couple of systems I have at hand here:

  • Proxmox VM-guest, where the host has 4x10000RPM drives in RAID 10: 155-160 MB/s
  • WDC WD2002FAEX-007BA0 HDD (2 of them in RAID 1): 102 MB/s
  • INTEL SSDSC2BB080G4 SSD: 97 MB/s
  • Proxmox VM-guest, where the host has 5x5400RPM drives in ZFS: 800-1600 MB/s

As you can see the lowest speed comes from a SSD drive, and is quite similar to what you see…


Hi Evert,

Thank you for your answer!
It looks like the operator told me the truth: it is SSD…
My best knowledge (and test on my own machine) SSD speed suppose to be close to 400-450MB/s.
Still wonder why the SSD speed is that low (RAID 1 HDD transfer rate higher than an SSD) and how to improve it (by the operator)…