SAS Single Path Configuration

A P P E N D I X A

This appendix describes special instructions to configure SAS single path connections between a data host running Solaris 10 operating system and a StorageTek 2530 Array.

It is not recommended to have a single controller, single path configuration when uptime and availability are key concerns or requirements.

Note - Multipath and single path configurations are supported for all StorageTek 2500 Series Arrays. Oracle recommends multipath configurations for data availability.

Note - Enclosure Service Modules (ESMs) cannot be used with a duplex 25xx array.

This appendix includes the following main sections:

Planning for SAS Single Path Connections

Configuring Single Path Connections

Verifying Single Path Information After Replacing Controllers

Planning for SAS Single Path Connections

Key requirements to configuring Solaris SAS single path are:

Configuring one host per initiator

Following the suggested file naming conventions

Editing the sd.conf file

Important Notes

Single-path can be achieved in either a simplex or duplex configuration.

Use Common Array Manager for the host type.

Viable options for connecting single path include:

Connect only one initiator to controller A for single host.

For a two-host configuration: Connect one initiator from first Host to first Controller and one initiator from second Host to second Controller.

Before configuring single path, you need to collect host, initiator, and topology information, review the naming conventions, and prepare a table of configuration information as outlined in the sections that follow.

Solaris 10 Restrictions

Solaris 10 OS does not dynamically discover volumes.

You might have to edit the sd.conf file to recognize the new or undiscovered volumes as documented in this chapter.

On Solaris 10 OS, the Target ID is generated from the World Wide Names (WWNs) of both the HBA initiators and the controller ports. Replacing controllers can change the Target ID. Review the file naming after changing controllers to make sure the naming conventions for single path in this document are still met.

Collecting Host Information

1. Issue the hostname command to collect the host information.

# hostname
 hostA
 
 # hostname
 hostB

This example uses two data hosts running Solaris 10 OS.

Collecting Initiator Information

An initiator is a system component that initiates an I/O operation over a Fibre Channel (FC) network. If allowed by FC fabric zoning rules, each host connection within the FC network has the ability to initiate transactions with the storage array. Each host in the FC network represents a separate initiator; therefore, if a host is connected to the system through two host bus adapters (HBAs), the system identifies two different negotiators (similar to multi-homed, Ethernet-based hosts). In contrast, when multipathing is used in round-robin mode, multiple HBAs are grouped together and the multipathing software identifies the group of HBAs as a single initiator.

1. Issue the dmesg command to collect initiator information (the initiator of data on the HBA).

# dmesg | grep WWN
 Apr  9 17:02:26 hostA     mpt1: Port 0/PHYs 0-3 (wide-port) WWN: 0x500605b000253410
 Apr  9 17:02:26 hostA     mpt1: Port 1/PHYs 4-7 (wide-port) WWN: 0x500605b000253414
# dmesg | grep WWN
 Apr  9 17:00:38 hostB     mpt3: Port 0/PHYs 0-3 (wide-port) WWN: 0x500605b0000db020
 Apr  9 17:00:38 hostB     mpt3: Port 1/PHYs 4-7 (wide-port) WWN: 0x500605b0000db024

In each of the above lines in the output is embedded valuable information as shown in the following example:

mpt3: Port 0/PHYs 0-3 (wide-port) WWN: 0x500605b0000db020

mpt3 - HBA

Port 0 - Port 0 or 1. Both PCI-X and PCIe HBAs are dual ported.

PHYs 0-3 - Each physical port has 4 channels (numbered 0 - 3) and is called PHY in SAS terminology

WWN: 0x500605b0000db020 - the World Wide Name. Note the last four digits.

Note - The initiator information is printed at boot-up time. If the dmesg command does not return any output, the same information can be obtaining by searching on the WWN string in the /var/adm/messages files.

Collecting Controller and Target ID Information

Use the cfgadm -al command to collect information about the controllers and the Target ID. The scsi-bus code identifies the SAS controller.

# cfgadm -al
Ap_Id                          Type         Receptacle   Occupant   Condition
c0                             scsi-bus     connected    configured unknown
c0::dsk/c0t0d0                 disk         connected    configured unknown
c0::dsk/c0t1d0                 disk         connected    configured unknown
c5                             scsi-bus     connected    configured unknown
c5::dsk/c5t9d0                 disk         connected    configured unknown
c5::es/ses2                    disk         connected    configured unknown
c6                             scsi-bus     connected    configured unknown
c6::dsk/c6t9d0                 disk         connected    configured unknown
c6::es/ses3                    disk         connected    configured unknown
unconfigured ok

Planning the Cabling Topology

The StorageTek 2540 Array, with a Fibre Channel data path, has built-in drivers with dynamic discovery and multipathing capabilities.

The StorageTek 2530 Array, if configured for SAS single path, does not have these capabilities. There is no utility to correlate the connections between initiators, HBA ports and controller ports. You have to plan the topology prior to configuring single path connections.

FIGURE A-1 Topology of the 2530 array when connected to data hosts

Figure showing two dual port HBAs connected to 2530 array controllers.

Suggested Naming Convention in the Sun Storage Common Array Manager Software

The following suggests an optional naming convention to assure the initiators are mapped correctly to the volumes. You can use the naming modifications listed in TABLE A-1 in the Sun Storage Common Array Manager software to improve the operations.

TABLE A-1 Naming Modifications in the Sun Storage Common Array Manager Software
CAM Components	Solaris Single Path Configuration	Naming Modification	Comments
Initiator names	Naming modifications 1. Start with the letter i- to denote that this is an initiator 2. Add data host name (example - hostA) 3. Add the HBA controller information (example - mpt1) 4. Add the last 4 characters of the WWN (example - 3410)	Start with i- Add naming of associated components.	Example - i-hostA-mpt1-3410 i-hostA-mpt1-3414 and i-hostB-mpt3-b020 i-hostB-mpt3-b024
Hosts	The initiator is associated with a particular: * Data host (example - hostA) * HBA controller (example - mpt1) * Initiator Port WWN (last four letters, example - 3410)	Start with vh- (for virtual host) Add naming of associated components.	Example - vh-hostA-mpt1-3410 vh-hostA-mpt1-3414 and vh-hostB-mpt3-b020 vh-hostB-mpt3-b024
Host Groups	In CAM, create one host (virtual host) per initiator The host is associated with a particular: * Data host (example - hostA) * HBA controller (example - mpt1) * Initiator Port WWN (last four letters, example - 3410)	Start with hg- (for host group) Add data host name	Example - hg-hostA hg-hostB
Host Group Restrictions	Include all hosts in the host group with the corresponding data host name.	Naming modifications Start the volume name with either A- or B- to denote which controller is the preferred controller.	Example - hg-hostA contains vh-hostA-mpt1-3410 and vh-hostA-mpt1-3414 hosts and hg-hostB contains vh-hostB-mpt3-b020 and vh-hostB-mpt3-b024 hosts.
Volumes		Ensure that all volumes beginning with A- are owned by Controller A and all volumes beginning with B- are owned by Controller B.	Example - A-vol1, A-vol2 and so on to denote that these volume's preferred owner is Controller A.
Mapping Volumes to Hosts	Map volumes to a host group, not to a host. (This maps the volume to all hosts in the host group.) Note - it is especially important with single path that ownership be correct as failover will not occur as it does with multipath.	Naming modifications Start the volume name with either A- or B- to denote which controller is the preferred controller.	Example - Map A-vol1 to hg-hostA instead of to vh-hostA-mpt1-3410

Completing the Configuration Worksheet

Whether you use the suggested naming strategy or not, you can use the following table as a guideline when collecting all information prior to configuring single path connections.

TABLE A-2 Collect Configuration Information
Component Type	Component Name	Your Value	Example	Result to Add to CAMC
Data host	# hosts		2	This information translates to the host groups
	Data host1		hostA	Host group 1 = hg-hostA
	Data host2		hostB	Host group 2 = hg-hostB
Initiators	# of HBAs in data host1		1	This information translates into initiator names and virtual host names. See Figure A-3.
	Initiator 0 WWN, last 4 characters, HBA controller		0x500605b000253410, 3410, mpt1	Initiator 1 = i-hostA-mpt1-3410 Virtual host 1 = vh-hostA-mpt1-3410
	Initiator 0 WWN, last 4 characters		0x500605b000253414, 3414, mpt1	Initiator 2 = i-hostA-mpt1-3414 Virtual host 2 = vh-hostA-mpt1-3414
	# of HBAs in data host2		1	-
	Initiator 0 WWN, last 4 characters		0x500605b0000db020, b020, mpt3	Initiator 3 = i-hostB-mpt3-b020 Virtual host 3 = vh-hostB-mpt3-b020
	Initiator 0 WWN, last 4 characters		0x500605b0000db024, b024, mpt3	Initiator 4 = i-hostB-mpt3-b024 Virtual host 4 = vh-hostB-mpt3-b024
Volumes to be owned by Controller A	# of volumes		3	Ensure that during mapping to a particular host group, the volumes are owned by Controller A. See Figure A-4.
	Volume 1 name		A-vol1
	Volume 2 name		A-vol2
	Volume 3 name		A-vol3
Volumes to be owned by Controller B	# of volumes		2	Ensure that during mapping to a particular host group, the volumes are owned by Controller B.
	Volume 4 name		B-vol1
	Volume 5 name		B-vol2
	Volume 6 name

Configuring Single Path Connections

With the information collected, you can now proceed to make the connections and configure the software for single path connections as documented in the following sections:

Connecting the Host and Array

Configuring Storage in the Sun Storage Common Array Manager Software

Identifying the Target ID

Adding More Devices

Connecting the Host and Array

1. Run the /usr/sbin/devfsadm command to disoover devices and load the appropriate driver (if necessary) on the host:

Physically connect the cables for your specific topology.

Issue the following command once from each of the data hosts:

# /usr/sbin/devfsadm

#

If no output displays, the command ran successfully.

2. Log into the Sun Storage Common Array Manager software as outlined in the Sun Storage Common Array Manager Software Installation Guide.

3. On the New Initiator page, view existing WWNs of initiators in Sun Storage Common Array Manager software.

Configuring Storage in the Sun Storage Common Array Manager Software

Follow the usual steps to configure storage in the Sun Storage Common Array Manager software. You can use the suggested naming conventions as you configure.

Before you begin, review the following configuration notes:

Do not map volumes to the hosts you created. Map the volumes only to host groups. If you map to hosts, you will have to change the mappings if you switch to a multipath configuration.

When mapping multiple volumes, assign the first volume LUN number 0. A Solaris 10 data host does not need any changes to recognize LUN 0 of a target. The procedure to identify the target depends on this step.

LUN 31 (named Access) is the UTM LUN and cannot be used. The UTM LUN is reserved for in-band RAID management.

Ensure volumes are on the preferred controllers. Example - set all volumes named with the prefix A- to be owned by Controller A.

Configuring Storage in the Management Software

Use the Sun Storage Common Array Manager software to configure the following:

Host groups

Creating one host for every initiator

Adding hosts to host groups

Creating volumes and associated objects using the Volume Creation Wizard.

Mapping the volumes to host groups

For more information, review the Online Help.

Adding More Devices

Before the host can see more devices, identify the Target ID and update the /kernel/drive/sd.conf file as noted in the following sections:

Identifying the Target ID

Updating the /kernel/drv/sd.conf File

Identifying the Target ID

1. Ensure that LUN ID 0 is mapped to a data host correctly as requested in Configuring Single Path Connections.

2. Identify the controllers and Target ID using the cfgadm command, noting which elements have the proper bus.

# cfgadm -al
Ap_Id 	Type         Receptacle   Occupant   Condition
c0 	scci-bus     connected    configured   unknown
c0::dsk/c0t0d0 	disk         connected    configured   unknown
c0::dsk/c0t1d0 	disk         connected    configured   unknown
c5 	scci-bus     connected    configured   unknown
c5::dsk/c5t9d0 	disk         connected    configured   unknown
c5::es/ses2 	disk         connected    configured   unknown
c6 	scci-bus     connected    configured   unknown
c6::dsk/c6t9d0 	disk         connected    configured   unknown
c6::es/ses3 	disk         connected    configured   unknown
unconfigured ok

Updating the `/kernel/drv/sd.conf` File

1. Edit the /kernel/drv/sd.conf file. Add any additional LUNs for the Target ID.

Note - Add LUN entries to the targets for each of your configured volumes. Adding unnecessary LUN entries to this file will increase boot time.

# 
 name="sd" parent="mpt" target=9 lun=0;
 name="sd" parent="mpt" target=9 lun=1;
 name="sd" parent="mpt" target=9 lun=2;
 name="sd" parent="mpt" target=9 lun=3;
  [ .. ]
 
 name="sd" parent="mpt" target=9 lun=30;

Note - LUN 31 (the UTM LUN) cannot be used. Do not add it to the sd.conf file.

2. Reboot the array to place the changes to sd.conf file into effect.

  # reboot -- -r

After reboot, you should be able to see the volumes.

3. Review devices using the format command.

In the format command output for each controller, you should be able to see the Target ID and the LUN. In the example below for controller 5 (c5t9d0), the Target ID is 9 and the LUN is 0.

 
# format
Searching for disks...done
 
 
c3t9d0: configured with capacity of 40.00GB
AVAILABLE DISK SELECTIONS:
0. c0t0d0 <SUN72G cyl 14087 alt 2 hd 24 sec 424>
/pci@1f,700000/pci@0/pci@2/pci@0/pci@8/LSILogic,sas@1/sd@0,0
1. c0t1d0 <SUN72G cyl 14087 alt 2 hd 24 sec 424>
/pci@1f,700000/pci@0/pci@2/pci@0/pci@8/LSILogic,sas@1/sd@1,0
2. c5t9d0 <SUN-LCSM100_S-0617 cyl 20478 alt 2 hd 64 sec 64>
/pci@1f,700000/pci@0/pci@9/LSILogic,sas@0/sd@9,0
...

4. Before using the volumes, you must label the disks using the format command.

5. After labeling the disk, verify the labels by looking at the detailed partition table using the format verify option.

Troubleshooting Errors When Trying to Establish Communication

If you get an error when attempting to write the label and/or when you are trying to write to a device specifically in a dual controller configuration, it is likely the LUN is currently owned by the controller that the host is not connected to.

If this occurs, go to the Volume Details Page for the volume associated with this LUN and change the owner.

Verifying Single Path Information After Replacing Controllers

Take the following steps to ensure smooth continuation of operations when replacing controllers.

On Solaris 10 OS, the Target ID is generated by using the World Wide Names of both the HBA initiators and the controller ports. When replacing controllers, there is a very high possibility that the Target ID will change. Therefore, caution must be exercised when replacing controllers.

Prior to replacing the controller, note how and where the devices are being used. Typically, a system administrator will either use the devices as raw devices or create file systems on them. When a file system is created, the mount point information is typically placed in the /etc/vfstab file.

Updating Single Path Information After Replacing Controllers

1. After replacing the controller, follow the steps to identify the new Target ID in Identifying the Target ID and Updating the /kernel/drv/sd.conf File.

2. Make changes to /etc/vfstab and any other places to reflect the change in the Target ID.