Hello all,

Setup information:

Openstack Version: Newton

1 KVM Controller on Server 1

1 KVM Cinder on Server 2. Server 2 has attached SSD of 120G as a block device(haven't created any file-system on SSD )

1 Compute node, Server 3

I have a pass-through configuration for SSD on Cinder VM and I can see the drive mounted as /dev/vda I have created an OpenStack instance on Compute node, let's call it VM-1. A Cinder volume is being attached to it and its mounted as /dev/vdb on VM-1.

Issue: I am seeing a very low disk Read/writes numbers for the mounted volume on VM-1.

Troubleshooting and HDPARM numbers till now:

1) SERVER 2(host for Cinder VM):

hdparm -Tt /dev/sda (SSD mount point)

Timing cached reads:   14808 MB in 
2.00 seconds = 7411.80 MB/sec

Timing buffered disk reads: 1208 MB in  3.00 seconds = 402.03 MB/sec

2) CINDER VM (on Server 2):

hdparm -t -direct /dev/vda 

/dev/vda: 
 Timing cached reads:   14136 MB in  1.98 seconds = 7125.59 MB/sec 
 Timing buffered disk reads: 1196 MB in  3.00 seconds = 398.15 MB/sec

3) VM-1 (on Server 3):

hdparm -t --direct **/dev/vdb**

/dev/vda: 
 Timing O_DIRECT disk reads: 208 MB in  3.01 seconds =  69.10 MB/sec

You can see there is a huge difference in disk reads in #2 and #3. Both the servers (server 2 and 3) are connected by 1000Mbps link. But, I found something strange when I checked network interfaces for the VM-1 on compute node(server 3).

ETHTOOL for eth0 (physical interface on Server3)

...
            Advertised pause frame use: Symmetric
            Advertised auto-negotiation: Yes
            *Speed: 1000Mb/s*
            Duplex: Full
            Port: Twisted Pair
...

ETHTOOL for TAP interface attached to VM-1:

...
            Supports auto-negotiation: No
            Advertised link modes:  Not reported
            Advertised pause frame use: No
            Advertised auto-negotiation: No
            **Speed: 10Mb/s**
            Duplex: Full
            Port: Twisted Pair
            PHYAD: 0
            Transceiver: internal
            Auto-negotiation: off
  ...

Interface speeds show huge difference here as well. Please suggest if there is any way I can change this speed on tap interface. Is there any configuration file or anything where I can specify this?

Looking forward for expert advice.

EDIT 1: Corrected VM-1's device name for Cinder Volume.

TIA