Multipath Io Setup - IBM TotalStorage DS300 Best Practices Manual

In the example a single iSCSI volume is present. This volume appears also at the
end of /proc/scsi/scsi as shown in Example 7-6.
Example 7-6 contents of /proc/scsi/scsi with no multipath
danube:~ # cat /proc/scsi/scsi
Attached devices:
Host: scsi0 Channel: 00 Id: 00 Lun: 00
Vendor: IBM
Type:
Host: scsi0 Channel: 00 Id: 08 Lun: 00
Vendor: IBM
Type:
Host: scsi2 Channel: 00 Id: 02 Lun: 00
Vendor: IBM
Type:
danube:~ #
Important: Because of variations in process scheduling and different network
delays, iSCSI volumes may be mapped to different SCSI device names every
time linux-iscsi is started. Ensure to use some form of persistent device
naming (like udev) if you use more than a single iSCSI LUN. Take also into
account that the SCSI host number changes for iSCSI devices when
linux-iscsi is restarted.
The device is now ready for use. It can be partitioned and formatted.

7.9.2 Multipath IO setup

In this section we describe how to setup a multipath configuration with the device
mapper multipath module of the Linux kernel, and the multipath-tools user-space
package. SLES9 SP2 or higher is necessary for this configuration.
Important: We show that device mapper and the multipath-tools can be used
for multipathing of iSCSI targets. We tested this configuration successfully in
our lab setup and show the possibilities of device mapper. However, this
configuration is not supported by IBM.
Before going further using device mapper multipath IO (DM MPIO), it is strongly
recommend to read through Novell's paper How to Setup/Use Multipathing on
SLES, which is online at the following URL:
http://portal.suse.com/sdb/en/2005/04/sles_multipathing.html
It is necessary to have the following packages installed to use DM MPIO:
Model: VIRTUAL DISK IM Rev: 1998
Direct-Access
Model: 25P3495a S320 1 Rev: 1
Processor
Model: DS300
Direct-Access
ANSI SCSI revision: 02
ANSI SCSI revision: 02
S320 Rev: 6.21
ANSI SCSI revision: 04
Chapter 7. TotalStorage DS300 installation
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