Logical units and target ports on IBMFlashSystem systems

For IBMFlashSystem, logical units are enumerated devices that have the same characteristics as LUNs.

LUNs

The IBMFlashSystem system has a maximum LUN size of 40 TB.

The IBMFlashSystem system can export 512 LUNs to the system, which is the system limit. The system supports greater than 2 TB LUNs.

LUN IDs

The IBMFlashSystem system identifies exported logical units through SCSI identification descriptor type 3. The 64-bit NAA IEEE Registered Extended Identifier (NAA=6) for the logical unit is in the form 6-OUI-VSID. For example, the model 9840-AE1 IEEE company ID is 005076 (IBM). The remaining part of the company ID is a vendor-specific ID.

 # lsmdisk 121
id 121
name mdisk121
status online
mode managed
mdisk_grp_id 8
mdisk_grp_name texan2
capacity 50.0GB
quorum_index 
block_size 512
controller_name texan2
ctrl_type 4
ctrl_WWNN 500507605EBFECC0
controller_id 19
path_count 32
max_path_count 32
ctrl_LUN_# 000000000000000D
UID 6005076001810000000000001900001b00000000000000000000000000000000
preferred_WWPN 
active_WWPN many
fast_write_state empty
raid_status 
raid_level 
redundancy
strip_size 
spare_goal
spare_protection_min
balanced 
tier generic_hdd
slow_write_priority
fabric_type fc
site_id 
site_name 
 #

Configuration, logical drives, and hosts

Use the default settings unless you need to use specific values. The IBMFlashSystem wizard provides a default storage pool from which the volumes can be provisioned. If you are using the command-line interface (CLI), enter the following command:

svctask mkarray -level raid0/5

A storage pool is provisioned automatically from which the volumes can be provisioned and presented to the system.

Generally, it is best to provide a few large LUNs to system (4 or 8) from the available capacity.

For more information, see the following IBM Redbooks publication:

http://www.redbooks.ibm.com/redbooks.nsf/redbookabstracts/tips1079.html?Open&c4#contents

LUN presentation

LUNs are exported through the available FC ports of the IBMFlashSystemstorage system. Do not use the default open mapping unless system guarantees sole access to the IBMFlashSystem. Use explicit host masking for the LUNs. Explicit is the preferred and safest method. See the information about the IBMFlashSystem command:

svctask chsystem -openaccess off

Special LUNs

You do not need to make special considerations for logical unit numbering. LUN 0 can be exported where necessary.

Target ports

An IBMFlashSystemstorage system can have a total of 16 8 GB Fibre Channel ports.

The following example shows the Fibre Channel ports on a controller:

 # lscontroller
id controller_name ctrl_s/n             vendor_id            product_id_low       product_id_high
19 texan2          000060400000-0000-0  IBM                  FlashSys             tem-9840

# lscontroller 19
id 19
controller_name texan2
WWNN 500507605EBFECC0
mdisk_link_count 15
max_mdisk_link_count 512
degraded no
vendor_id IBM
product_id_low FlashSys
product_id_high tem-9840
product_revision 1103
ctrl_s/n 000060400000-0000-0 
allow_quorum yes
fabric_type fc
site_id 
site_name 
WWPN 500507605EBFECE4
path_count 120
max_path_count 4096
WWPN 500507605EBFECC4
path_count 120
max_path_count 4096
WWPN 500507605EBFECD4
path_count 120
max_path_count 4096
WWPN 500507605EBFECF4
path_count 120
max_path_count 409
 #

Model 9840-AE1 WWNN and WWPN settings are displayed as shown in the following example:

5005076SSSSSSSPP
5                  -   IEEE 803.2  ID NAA format,
005076       -   IEEE unique VSID for IBM. (common with SVC)
SSSSSS      -   unique vendor-supplied serial number for the device. 
PP              -  vendor specific code used to identify specific ports 
WWNN 500507605EBFF2C0 
WWPN 500507605EBFF2E1 
WWPN 500507605EBFF2D1 
WWPN 500507605EBFF2C1 
WWPN 500507605EBFF2F1

LU access model

All systems are Active/Active. To avoid an outage from system failure, cross connect the ports across Fibre Channel switches. Because all IBMFlashSystemstorage systems are equal in priority, you gain no benefit by using an exclusive set for a specific LU.

LU preferred access port

No access ports are preferred on the IBMFlashSystem system because all ports are Active/Active across all systems.

Detecting Ownership

Detecting ownership does not apply to IBMFlashSystem storage arrays.