Revision as of 12:53, 31 October 2016

Overview

Mellanox added iSCSI Extensions for RDMA (iSER) that does not need the TCP layer. Therefore, it provides lower latency and higher performance.
It permits data to be transferred directly into and out of SCSI computer memory buffers, which connects computers to storage devices, without intermediate data copies.
iSER is a server network protocol that extends the Internet Small Computer System Interface (iSCSI) protocol to use Remote Direct Memory Access (RDMA).

Please contact Mellanox for further information and benchmark results.

Installation

Provisioned through standard Cinder installation.

Configuration

In order to enable iSER, adjust these values at /etc/cinder/cinder.conf:

iscsi_ip_address = <ipoib/roce_address>
iscsi_protocol = iser
volume_driver = cinder.volume.drivers.lvm.LVMVolumeDriver

iscsi_ip_address is required to do a "discovery" over the IB/RoCE interface from the initiator side.

volume_driver points cinder to use the LVMVolumeDriver.

Restart Cinder service

#/etc/init.d/openstack-cinder-volume restart

For troubleshooting issues, refer to section Known Issues

Known Issues

(1) “scsi-target-utils” package

Note: For RH6.4 or below, “scsi-target-utils” package version needs to be 1.0.38 and above. If you use RDO installation, you should check the version. The RPM can be found at http://www.mellanox.com/downloads/solutions/rpms/

#wget http://www.mellanox.com/downloads/solutions/rpms/scsi-target-utils-1.0.39-v1.0.39.c1135a.x86_64.rpm
#rpm -Uvh scsi-target-utils-1.0.39-v1.0.39.c1135a.x86_64.rpm

In addition, RH6.5 includes “scsi-target-utils” package with version 1.0.24-10. This version number is sufficient and no further action is needed for RHEL6.5.

(2) Boot Instance from volume fails when iSER is enabled.

Steps to reproduce the bug:

- Create new volume with image source.

- Launch a new instance boot from the above volume using iSER transport.

The bug is defined here: [1]

A patch can be found here: [2]

To apply the patch, run the following commands on all nova-compute nodes:

# wget http://www.mellanox.com/downloads/solutions/openstack/havana/patches/volume.patch 
# patch -p1 < volume.patch
# service nova-compute restart 

(3) Flow control

In case the network is Ethernet, make sure that flow control is enabled on the switches on the relevant ports across the network.

(4) Linux-IO (LIO) support limitation.

Open-source implementation of SCSI target in Openstack can be managed by either TGT or LIO.
Currently in Openstack, iSER is supported over TGT only, and iSER support over LIO is scheduled for Kilo version.
In case LIO is the default SCSI target, one must one install TGT and alter Openstack Cinder conf file to use TGT instead of lio.

References

1. OpenStack solution page at Mellanox site

2. Source repository

3. Mellanox OFED web page

4. Cinder-controller

5. Cinder-node

Return to Mellanox-OpenStack wiki page.

For more details, please refer any inquiries to openstack@mellanox.com.