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NexentaStor
TM
Target FC and Host Multipathing
NexentaStor Release 3.1.x
Target FC and Host Multipathing
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Document revision number: 2
Date: August 26, 2011
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Target FC and Host Multipathing
Table of Contents
1 Introduction...............................................................................................................................5
1.1 Terminology.......................................................................................................................6
1.2 Installation .......................................................................................................................6
2 Examples of implementation....................................................................................................9
2.1 Setting up NexentaStor multipathing mode for Windows Server 2008 R2.......................9
2.2 Setting up NexentaStor multipathing on Linux-based OS..............................................19
3 References..............................................................................................................................21
4 Contact information.................................................................................................................23
4.1 Support request ..............................................................................................................23
4.2 Other resources...............................................................................................................24
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1 Introduction
Multipath I/O, or multipathing is a method to increase fault-tolerance and bandwidth
performance. It provides multiple physical paths between the CPU in a computer system and
its mass storage devices through the host bus adapters, controllers, switches, and bridge
devices connecting them. Multipathing reduce the risk of a single point of error and let system
administrator to set up multiple routes between the server and storage.
A simple example would be a SCSI connected to two SCSI controllers on the same computer
or a disk connected to two disk ports. If one of the component in this net work fails, the
operating system can route I/O through the remaining transparently to the application, with no
changes visible to the users, other than additional timeout.
Fibre Chanel multipathing operates on low hardware level. Multipath software layers can
leverage the usage of redundant paths to provide performance enhancing features, such as
load balancing and traffic shaping.
The following diagram represents the main idea of Fibre Chanel multipathing.
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Currently, NexentaStor supports multipathing for Fibre Channel connections using supported
SAS HBAs. With the help of Target FC plugin NexentaStor 3.0 can be turned to a fully
compliant FC target (see section '3. References' for more info about NexentaStor plugins).
1.1 Terminology
There are some basic terms, which need to be defined before starting multipathing
configuration.
Term
Initiator
Target
Fibre Chanel
1.2
Definition
Host, or client, that initiates a SCSI session, that is,
sends a SCSI command.
Endpoint that does not initiate sessions, but instead
waits for initiators' commands and provides required
input/output data transfers. The target usually
provides to the initiators one or more LUNs.
A gigabit-speed network technology primarily used
for storage networking.
Installation
To start with configuring FC multipathing you need to install the corresponding scsitarget
plugin (depending on your NexentaStor version).
Run in NMC:
nmc:/$ setup plugin install <PUGIN NAME>
or install plugin via GUI: Settings → Appliance → Plugins:
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2 Examples of implementation.
2.1 Setting up NexentaStor multipathing mode for Windows Server
2008 R2.
1. Connect all the hardware. After installing FibreChannel HBAs in the system, the
associated on the HBAs ports will automatically appear in the GUI.
2. On the Windows server, install appropriate management software for the Fibre
Channel configuration (the software typically comes in a package with the FC
HBAs).
3.
•
Enable MPIO feature on Windows Server:
Open Server manager and choose 'Features'.
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•
In a pop-up window check 'Multipath I/O'
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•
Click on 'Install' on the next screen:
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•
After successful installation, the following screen appears.
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•
Later MPIO can be launched from 'Administrative Tools'
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4. Set up zvol on NexentaStor via NMC:
nmc:/$ setup zvol create
or via NMV (Data Management → SCSI target → Zvols →Create):
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5. Create Initiator group for more security:
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6. Create LUN Mappings (see 'NexentaStor SCSI Target' documentation for details):
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7. On the Windows side, run MPIO: press 'Start' and type “MPIO” in search tab.
8. Go to 'Discover Multi-Paths' - under Device Hardware ID. You should see
'NEXENTA COMSTAR' in the listing.
9. Press 'Add'. This operation requires reboot.
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10. After reboot you should see 'NEXENTA COMSTAR' in the list of devices
11. Open Administrative tools → Server management → Disk Management
12. Disks are available now – just need to be initialized.
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2.2 Setting up NexentaStor multipathing on Linux-based OS.
With most of Linux-based OS you will have to deal with editing multipath.conf - multipath
daemon configuration file.
The following basic steps represent how to enable multipath mode for Red Hat Enterprise
Linux 4:
1. Connect all the hardware. After plugging in Fibre Channel HBAs in the system, the
associated on the HBAs ports will automatically appear in the GUI.
2. Follow the steps 4-6 from section 2.1.Setting up NexentaStor multipathing mode for
Windows Server 2008 R2 to create a zvol and LUN mappings.
3. Make sure, that 'device-mapper-multipath' package is installed on the host.
4. multipath.conf need to be edited as follows:
As far as all devices are blacklisted by default, the following lines are need to be
commented out to enable multipathing:
# devnode_blacklist {
#
devnode "*"
# }
You can change any of the 'defaults', such as user_friendly_name as per your own
configuration needs. When it's done, save and exit.
5. Start multipathing daemon by running the following commands:
# modprobe dm-multipath
# service multipathd start
6. Check, if multipath daemons start on boot:
# chkconfig multipathd on
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7. To list multipathed devices, run the command:
# multipath -ll
You should receive the output like:
mpath0 (3600144f0ee48850000004c765d440001) dm-2
NEXENTA,COMSTAR
[size=10G][features=0][hwhandler=0][rw]
\_ round-robin 0 [prio=1][enabled]
\_ 1:0:0:0 sda 8:0 [active][ready]
\_ round-robin 0 [prio=1][enabled]
\_ 0:0:0:0 sdb 8:16
[active][ready]
\_ round-robin 0 [prio=1][enabled]
\_ 1:0:3:0 sdc 8:32
[active][ready]
\_ round-robin 0 [prio=1][enabled]
\_ 0:0:3:0 sdd 8:48
[active][ready]
8. The device can now be accessed (in the above example) using the path
/dev/mapper/mpath0
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3 References
•
Target FC product web-page
•
Target 2.0 product web-page
•
Check Documentation 3.x and Documentation 2.x pages on www.nexenta.com for
Target FC and Target 2.0 user manuals.
F.A.Q. articles:
•
What does the term SCSI Target mean?
•
SCSI target: how to disable disk caching (NexentaStor v3.x)
•
Can NexentaStor act as an iSCSI or Fibre Channel target?
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4 Contact information
4.1 Support request
To contact support at Nexenta Systems, click on 'Support' in NMV as it's marked with red
square on the screen bellow.
or type the following NMC command:
nmc:/$ support
which will then prompt for a subject and message.
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4.2 Other resources
For licensing questions, please email to sales@nexenta.com
For more advanced questions related to the product, be sure to check our FAQ for the latest
information.
Nexenta Systems has various professional services offerings to assist with installing and
managing the product. Training courses on high availability and other features of NexentaStor
are also available. For service and training offerings, check our website at
http://www.nexenta.com.
About Nexenta Systems
Founded in 2005 and privately held, Nexenta Systems, Inc., has developed
NexentaStor™, the leading open storage enterprise class hardware independent
storage solution and sponsors NexentaCore, an open source operating system
that combines the high performance and reliability of OpenSolaris with the ease-ofuse and breadth of applications of Linux. Both solutions leverage the revolutionary
file system ZFS. More information about Nexenta Systems, Inc. and free trials of
the ZFS-based NexentaStor can be found at www.nexenta.com or call:
(877) 862-7770.
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