SCSI over FCP for Linux on System z

SCSI over FCP
for Linux on System z
zLG09

Susanne Wintenberger

SCSI over FCP for Linux on System z

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Agenda

■ Introduction to FCP on System z
■ FCP with Linux on System z
■ IPL over FCP
■ SCSI dump
■ Multipathing
■ N-Port Id Virtualization (NPIV)
■ Troubleshooting



FCP in a Nutshell

■ Storage Area Networks (SANs) are specialized networks dedicated to the
transport of mass storage data
■ Today the most common SAN technology used is Fibre Channel Protocol (FCP)
■ With this technology the SCSI protocol is used to address and transfer raw data
between the servers and the storage device
■ Each server is equipped with a least one adapter which provides the physical
connection to the SAN
■ For System z any supported FCP adapter, such as FICON Express, FICON
Express2, FICON Express4 of FICON Express8 can be used for this purpose.
■ The Fibre Channel (FC) standard was developed by the National Committee of
Information Technology Standards (NCITS)



Why FCP?

■ Performance advantages ■ System z integration in existing FC
– FCP is much faster than FICON SANs
– Reason 1: asynchronous I/O ■ Use of existing FICON infrastructure
– Reason 2: no ECKD emulation – FICON Express adapter cards
overhead – FC switches / Cabling
■ No disk size restrictions – Storage subsystems
■ Up to 15 partitions (16 minor ■ Dynamic configuration
numbers per device) – Adding of new storage
■ SCSI disks do not waste disk space subsystems possible without
(no low-level formatting) IOCDS change
■ Does NOT require more CPU than
FICON



SAN topologies and System z

point-to-point direct attached
arbitrated loop switched fabric

not
supported

Disk Tape Disk Tape Disk Tape



FCP channel and subchannel

Linux connects through FCP
Linux
Linux
subchannels to FCP attached
storage.
FCP
FCP
subchannel
subchannel
FCP channel
FCP channel A subchannel is identified – in
Linux - by its bus identifier
which is derived from the
subchannel's device number.

sample FCP subchannel (as
seen in Linux):
/sys/bus/ccw/drivers/zfcp/0.0.1900



World Wide Port Names (WWPN)

Storage devices and servers
attach through Fibre Channel
Linux
Linux ports (called N_Ports).
FCP
FCP
other OS
other OS subchannel
subchannel
FCP
FCP FCP channel
FCP channel
An N_Port is identified by its
World-Wide Port Name
(WWPN).

For redundancy, servers or
storage may attach through
several N_Ports.

sample WWPN:
0x5005076303000104


Logical Unit Number (LUNs)

Storage devices usually
comprise many logical units
(volumes, tape drives, ...).

A logical unit is identified by its
Fibre Channel Protocol
Logical Unit Number (FCP
LUN).

sample FCP LUN:
0x4021400000000000
Beware of LUN translation!



Navigating in a SAN

Worldwide Port Name Logical Unit Number
FCP subchannel (WWPN) (LUN)
(”virt. Adapter”) e.g. e.g.
e.g. 0.0.1900 0x5005076303000104 0x4021400000000000



SCSI compared to Channel I/O

■ SCSI / FCP ■ Channel I/O
– Channel subsystem device – Channel subsystem device
represents the virtual adapter represents disk volume
to the Fibre Channel SAN (ECKD)
– FCP adapter is defined in – Device defined in System z I/O
System z I/O configuration configuration
– Ports and LUNs attachment – Ports attachment handled in
handled in Operating System z I/O configuration
Systems
– Multipathing handled in System z
– Multipathing handled in firmware
Operating System
– Disk size restrictions to Mod 54 /
– No disk size restrictions for SCSI Mod 224
disks
– Switch configuration via System
– Additional configuration outside z I/O configuration
System z necessary
• Zoning in the SAN
fabric
• LUN masking on the
11
storage server © 2012 IBM Corporation


ZFCP getting started

■ To access a Fibre Channel-attached SCSI device follow these configuration steps:
1) Configure a Fibre Channel host adapter within the mainframe (I/O Definition File).
2) Configure zoning for the Fibre Channel host adapter to gain access to desired
target ports within a SAN.
• Segmentation of a switched fabric is achieved though zoning. It can be used to
partition off certain portions of the switched fabric, allowing only the members of
a zone to communicate with that zone.
3) Configure LUN masking for the Fibre Channel host adapter at the target device to
gain access to desired LUNs.
• A LUN represents a portion of a controller, such as a disk device. With the use of
LUNs, a controller can be logically divided into independent partitions. Access to
this LUNs can be restricted to distinctive WWPNs as part of the controller
configuration
4) In Linux, configure target ports and LUNs of the SCSI device at the target
port for use of zfcp.
■ Note: If the Fibre Channel host adapter is directly attached to a target device
(point-to-point connection), step 2 is not needed.


Hardware: Define FCP adapter in IOCDS

CHPID PATH=(CSS(0,1,2,3),51),SHARED, *
NOTPART=((CSS(1),(TRX1),(=)),(CSS(3),(TRX2,T29CFA),(=)))*
,PCHID=1C3,TYPE=FCP
CNTLUNIT CUNUMBR=3D00, *
PATH=((CSS(0),51),(CSS(1),51),(CSS(2),51),(CSS(3),51)), *
UNIT=FCP
IODEVICE ADDRESS=(3D00,001),CUNUMBR=(3D00),UNIT=FCP
IODEVICE ADDRESS=(3D01,007),CUNUMBR=(3D00), *
PARTITION=((CSS(0),T29LP11,T29LP12,T29LP13,T29LP14,T29LP*
15),(CSS(1),T29LP26,T29LP27,T29LP29,T29LP30),(CSS(2),T29*
LP41,T29LP42,T29LP43,T29LP44,T29LP45),(CSS(3),T29LP56,T2*
9LP57,T29LP58,T29LP59,T29LP60)),UNIT=FCP
IODEVICE ADDRESS=(3D08,056),CUNUMBR=(3D00), *
PARTITION=((CSS(0),T29LP15),(CSS(1),T29LP30),(CSS(2),T29*
LP45),(CSS(3),T29LP60)),UNIT=FCP


Manual LUN configuration with s390-tools

Show available FCP devices:

# lscss -t 1732/03,1732/04
Device Subchan. DevType CU Type Use PIM PAM POM CHPIDs
----------------------------------------------------------------------
0.0.1900 0.0.0010 1732/03 1731/03 80 80 ff 3b000000 00000000
0.0.1940 0.0.0011 1732/03 1731/03 80 80 ff 46000000 00000000

Enable FCP devices:

# chccwdev -e 0.0.1900,0.0.1940
Setting device 0.0.1900 online
Done
Setting device 0.0.1940 online
Done

Show online FCP devices and corresponding SCSI hosts:

# lszfcp
0.0.1900 host0
0.0.1940 host1



Manual LUN configuration with s390-tools (cont'd)

Attach ports, only required for older distributions (SLES10, RHEL5, ...):

# echo 0x5005076303000104 > /sys/bus/ccw/drivers/zfcp/0.0.1900/port_add
# echo 0x5005076303100104 > /sys/bus/ccw/drivers/zfcp/0.0.1940/port_add

Show available storage ports:

# lszfcp -P
0.0.1900/0x5005076303000104 rport-0:0-8
0.0.1940/0x5005076303100104 rport-1:0-0

Attach LUNs:

# echo 0x4021400000000000 >
/sys/bus/ccw/drivers/zfcp/0.0.1900/0x5005076303000104/unit_add
# echo 0x4021400000000000 >
/sys/bus/ccw/drivers/zfcp/0.0.1940/0x5005076303100104/unit_add

List available LUNs:

# lszfcp -D
0.0.1900/0x5005076303000104/0x4021400000000000 0:0:8:1074872353
0.0.1940/0x5005076303100104/0x4021400000000000 1:0:0:1074872353


Linux Tools: lsscsi and lsluns

lsscsi: Show SCSI devices and block device nodes:

# lsscsi
[0:0:8:1074872353]disk IBM 2107900 .280 /dev/sda
[1:0:0:1074872353]disk IBM 2107900 .280 /dev/sdb

lsluns: Which LUNs are available on the storage system for use?

# lsluns -c 0.0.1900 -p 0x5005076303000104
Scanning for LUNs on adapter 0.0.1900
at port 0x5005076303000104:
0x4021400000000000
0x4021400100000000
0x4021400200000000
0x4021400300000000
0x4021400400000000
0x4021400500000000
0x4021400600000000
0x4021400700000000
0x4021400800000000
0x4021400900000000



zfcp configuration files

■ Configuring LUNs manually through sysfs is not persistent, will be lost after IPL
■ Use configuration mechanism provided by distribution for persistent LUN
configuration
■ See documentation from distributions for details
■ zfcp configuration file in RHEL
– /etc/zfcp.conf
■ zfcp configuration files in SLES 10
– /etc/sysconfig/hardware/hwcfg-zfcp-bus-ccw-*
■ zfcp configuration files in SLES 11
– /etc/udev/rules.d/51-zfcp*



SLES: GUI Setup

■ zfcp dialog in YaST simplifies setup
of SAN attached devices
■ Auto detects available
FCP subchannels, WWPNs, and
LUNs
■ copy&paste WWPNs and FCP_LUNs
from configuration file obtained
from SAN management tools or
administrator

■ alternatively on command line
– SLES 10: /etc/sysconfig/hardware/hwcfg-zfcp-bus-ccw-0.0.*
– SLES 11: zfcp_{host|disk}_configure → /etc/udev/rules.d/51-zfcp-
0.0.*.rules



RHEL: GUI Setup

■ Ignore subsequent complaints in
case of DASD-less system.
■ GUI only available during installation.
Define FCP devices in
/etc/zfcp.conf for permanent
addition.

# cat /etc/zfcp.conf
0.0.1900 0x5005076303000104 0x4021400000000000
# cat /etc/modprobe.conf (RHEL5)
alias scsi_hostadapter zfcp
# cat /etc/modprobe.d/local.conf (RHEL6)
alias scsi_hostadapter zfcp
# /sbin/zfcpconf.sh


zfcp: SCSI disk usage

# fdisk /dev/sda

Command (m for help): p

Disk /dev/sda: 5368 MB, 5368709120 bytes
166 heads, 62 sectors/track, 1018 cylinders
Units = cylinders of 10292 * 512 = 5269504 bytes

Device Boot Start End Blocks Id System
/dev/sda1 1 1018 5238597 83 Linux

# mke2fs -j /dev/sda1



SCSI IPL

■ The traditional initial program load (IPL) process relies on accessing a device
using System z channel attachment
■ For IPL from a FCP-attached device, this is not possible
■ SCSI IPL expands the set of IPL'able devices
– SCSI disks as Linux boot file system possible
■ New set of IPL parameters
■ Requires to address the SCSI disk
– FCP adapter id
– Remote port
– LUN
■ LPAR and z/VM guests supported
■ SCSI (IPL) with z/VM
– z/VM Version 4.4 (PTF UM30989) or newer
– z/VM Version 5.3 (current version)



SCSI IPL example LPAR



SCSI IPL example z/VM
In hexadecimal format with a
set loaddev port 50050763 03000104 lun 40214000 00000000 blank separating the first 8
Ready; T=0.01/0.01 22:11:01 from the final 8 digits

WWPN LUN
query loaddev
PORTNAME 50050763 03000104 LUN 40214000 00000000 BOOTPROG 0
BR_LBA 00000000 00000000
Ready; T=0.01/0.01 22:11:06 is the device number of the FCP subchannel
that provides access to the SCSI boot disk.
i 1900
00: HCPLDI2816I Acquiring the machine loader from the processor controller.
00: HCPLDI2817I Load completed from the processor controller.
00: HCPLDI2817I Now starting the machine loader.
00: MLOEVL012I: Machine loader up and running (version 0.18).
00: MLOPDM003I: Machine loader finished, moving data to final storage location.
Linux version 2.6.16-18.x.20060403-s390xdefault (wirbser@t2944002) (gcc version
4.1.0) #1 SMP PREEMPT Mon Apr 3 09:56:54 CEST 2006
We are running under VM (64 bit mode)
Detected 4 CPU's
Boot cpu address 0
Built 1 zonelists
Kernel command line: dasd=e960-e962 root=/dev/sda1 ro noinitrd zfcp.device=0.0.1900,
0x5005076303000104,0x4021400000000000



SCSI dump

■ Dump memory of one LPAR to disk for problem analysis
■ Similar to VMDUMP and dump to DASD
■ SCSI dump supported for LPARs and as of z/VM 5.4
■ Preparation summary:
– large SCSI disk (system memory + 11 MB)
– fdisk /dev/sda
– mke2fs /dev/sda1
– mount /dev/sda1 /mnt
– zipl -D /dev/sda1 -t /mnt
– umount /mnt



SCSI dump from HMC

■ Select CPC image for LPAR to dump
■ Goto Load panel
■ Issue SCSI dump
– FCP device ID
– WWPN
– LUN



SCSI dump under z/VM

■ SCSI dump from z/VM is supported as of z/VM 5.4
■ Issue SCSI dump

#cp cpu all stop
#cp cpu 0 store status
#cp set dumpdev portname 47120763 00ce93a7 lun 40104020 00000000
bootprog 0
#cp ipl 4b49 dump

■ To access the dump, mount the dump partition



FCP Multipathing

Linux
Linux

2 paths to disk through independent FCP adapters and independent controllers.



Multipathing for disks

■ Use multiple paths from operating system to storage
■ Why multipathing ?
– Avoid single points of failure
– Performance: I/O requests can be spread across multiple paths,
– Usually a requirement for SAN connected storage servers
• e.g. when one storage controller is in maintenance mode I/O continues to run
through second controller
■ Multipathing in Linux
– Implemented in Linux in multipath-tools package, together with the device-mapper in the
Linux kernel
– The default configuration is already included, configuration changes only for special
requirements
– SCSI device (“LUN”) in Linux represents one path to the disk volume on the storage server
■ Multipath devices are block devices in Linux, can be used e.g.
– Partitions
– Directly for a filesystem
28 – Logical Volume Manager (LVM) © 2012 IBM Corporation


Multipathing for disks – linux device mapper

The device mapper creates one block device for the LUN /dev/mapper/xxx
/dev/mapper/36005076303ffc56200000000000010cc

unique WWID
dm multipath

(World-Wide Identifier) from
/dev/sda /dev/sdb storage server identifies volume

Linux SCSI layer, zfcp

FCP adapter 1 FCP adapter 2



zfcp setup for multipathing

■ zfcp and SCSI report each path as device
■ multipathing happens on higher layer
■ avoid shared components in different paths

# lsscsi
[0:0:0:0] disk IBM 2107900 2.27 /dev/sda
[1:0:1:0] disk IBM 2107900 2.27 /dev/sdb
# lszfcp -D
0.0.3c00/0x500507630313c562/0x401040cc00000000 0:0:0:0
0.0.3d00/0x500507630303c562/0x401040cc00000000 1:0:1:0

different adapters and usually same
different ports to avoid FCP LUN (check
single points of failures on storage server)



Multipathing setup and configuration

■ Config file /etc/multipath.conf: Default settings are usually good, but can be
overwritten
■ Ensure devices are not blacklisted and multipathd is running
# cat /etc/multipath.conf
blacklist {
devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
devnode "^hd[a-z][[0-9]*]"
devnode "^cciss!c[0-9]d[0-9]*[p[0-9]*]"
devnode "^dasd[a-z]+[0-9]*"
}

■ Multipath devices are created automatically when SCSI LUNs are attached
WWID for # multipath -ll
volume 36005076303ffc56200000000000010cc dm-0 IBM,2107900
[size=5.0G][features=1 queue_if_no_path][hwhandler=0]
_ round-robin 0 [prio=2][active]
_ 1:0:0:0 sdb 8:16 [active][ready]
pathgroup _ 0:0:0:0 sda 8:0 [active][ready]
…


Multipathing setup and configuration (cont'd)

■ Device to work with: /dev/mapper/36005076303ffc56200000000000010cc

# mkfs.ext3 /dev/mapper/36005076303ffc56200000000000010cc
…
# mount /dev/mapper/36005076303ffc56200000000000010cc /mnt

■ Example: Change rr_min_io to 10 - (number of IO to route to a path before
switching to the next in the same path group)
■ See multipath.conf manpage and documentation from distributions for details

# cat /etc/multipath.conf
multipaths {
multipath {
wwid "36005076303ffc56200000000000010cc"
rr_min_io "10"
path_selector "round-robin 0"
}
}



Root filesystem on SCSI multipath volume

■ Possibility to put root filesystem on SCSI multipath volume
■ Older zipl versions do not support writing on multipath device
■ Workaround: Use additional single path volume for /boot, use this volume for IPL
■ Newer Linux distributions (e.g. SLES 11 SP1, RHEL 6.2) support root filesystem
on multipath device without workaround with s390-tools 1.8.3 or newer
■ http://www.ibm.com/developerworks/linux/linux390/s390-tools-1.8.3.html
– zipl: Add support for device mapper devices.
– zipl now allows installation of and booting from a boot record on logical devices,
i.e. devices managed by device mapper (or similar packages), e.g. multipath
devices.



N-Port Id Virtualization (NPIV)

NPIV
■ NPIV: Each virtual adapter has its
subchannels own WWPN in the SAN. This is
have a unique the foundation for restricting
WWPN for the FCP access to storage.
device
■ SAN zoning: Only WWPNs in
same zone can communicate
Non-NPIV ■ “LUN masking” or “host
subchannels
share one WWPN
connections”: Each disk volume
is only available for a specific
list of WWPNs
SAN Zoning: Only
WWPNs in the
■ With NPIV: Restricted configuration
same zone can possible where disk volumes
communicate are defined for each operating
system
“LUN masking” ■ Without NPIV: First operating
or “host system to access a disk volume
connections” can use it.


NPIV requirements

+ +
■ NPIV is available on System z9, System z10 and z/Enterprise
– FICON Express 2 adapter running with MCL003 on EC J99658
■ z/VM
– z/VM 5.2 or 5.3
– z/VM 5.1 with the PTF for APAR VM63744
■ Linux Distribution
– Currently SLES10, SLES11, RHEL5, RHEL6 (LPAR mode or z/VM)
■ NPIV-Capable Switch
– only required for switch adjacent to System z
– Mostly firmware upgrades possible (e.g. McData, Brocade)


NPIV

# lszfcp -a | grep port_name
permanent_port_name = "0xc05076ffe5005611"
port_name = "0xc05076ffe5005350"

■ “port_name” is the WWPN used by the FCP subchannel
■ “permanent_port_name” is the WWPN assigned to the FCP channel
■ Compare to find out if NPIV is in use:
– If both are the same, the FCP subchannel does NOT use NPIV
– If they differ, the FCP subchannel uses NPIV
■ Worldwide portname prediction tool
■ http://www.ibm.com/servers/resourcelink/



Troubleshooting

■ Check kernel messages that are possibly related to SCSI on Linux on System z:
– scsi (common SCSI code)
– sd (SCSI disk)
– rport (common SCSI code FC remote port messages)
– qdio (communication between Linux and FCP Channel)
– zfcp driver kernel messages
– See “Kernel Messages” book on
https://www.ibm.com/developerworks/linux/linux390/
– “device-mapper: multipath”
■ Other syslog messages
– Multipathd
■ zfcp driver traces available in /sys/kernel/debug/s390dbf/
■ Collect data with dbginfo.sh when reporting a problem to capture configuration,
messages and traces



Troubleshooting: scsi_logging_level

# scsi_logging_level -g ■ More SCSI output in kernel
Current scsi logging level: messages
dev.scsi.logging_level = 0
SCSI_LOG_ERROR=0 ■ Higher levels can create lots of
SCSI_LOG_TIMEOUT=0 messages and slow down system
SCSI_LOG_SCAN=0
SCSI_LOG_MLQUEUE=0 # scsi_logging_level -s -a 1
SCSI_LOG_MLCOMPLETE=0 New scsi logging level:
SCSI_LOG_LLQUEUE=0 dev.scsi.logging_level = 153391689
SCSI_LOG_LLCOMPLETE=0 SCSI_LOG_ERROR=1
SCSI_LOG_HLQUEUE=0 SCSI_LOG_TIMEOUT=1
SCSI_LOG_HLCOMPLETE=0 SCSI_LOG_SCAN=1
SCSI_LOG_IOCTL=0 SCSI_LOG_MLQUEUE=1
SCSI_LOG_MLCOMPLETE=1
SCSI_LOG_LLQUEUE=1
SCSI_LOG_LLCOMPLETE=1
SCSI_LOG_HLQUEUE=1
SCSI_LOG_HLCOMPLETE=1
SCSI_LOG_IOCTL=1



Troubleshooting: zfcp_show

■ Query Fibre Channel nameserver about ports available for my system:

# zfcp_show -n
Local Port List:
0x500507630313c562 / 0x656000 [N_Port] proto = SCSI-FCP FICON
0x50050764012241e4 / 0x656100 [N_Port] proto = SCSI-FCP
0x5005076401221b97 / 0x656400 [N_Port] proto = SCSI-FCP

■ Query SAN topology, requires FC management server access:
# zfcp_show

Interconnect Element Name 0x100000051e4f7c00
Interconnect Element Domain ID 005
Interconnect Element Type Switch
Interconnect Element Ports 256
ICE Port 000 Online
Attached Port [WWPN/ID] 0x50050763030b0562 / 0x650000 [N_Port]
ICE Port 001 Online
Attached Port [WWPN/ID] 0x50050764012241e5 / 0x650100 [N_Port]
ICE Port 002 Online
Attached Port [WWPN/ID] 0x5005076303008562 / 0x650200 [N_Port]
ICE Port 003 Offline
...


Troubleshooting: zfcp_ping

■ Check if remote port responds (requires FC management service access):

# zfcp_ping 0x5005076303104562
Sending PNG from BUS_ID=0.0.3c00 speed=8 GBit/s
echo received from WWPN (0x5005076303104562) tok=0 time=1.905 ms

---------- ping statistics -----------
min/avg/max = 1.905/2.249/2.447 ms
--------------------------------------

■ zfcp_show and zfcp_ping are part of the zfcp-hbaapi 2.1 package:
http://www.ibm.com/developerworks/linux/linux390/zfcp-hbaapi-2.1.html



Summary of FCP

■ available for zSeries and System z
■ based on existing Fibre Channel infrastructure
■ runs on all available z/VM and RHEL/SLES versions
■ integrates System z into standard SANs
■ connects to switched fabric or point-to-point
■ multipathing for SCSI disks is a must
■ gives you new storage device choices
■ usually performs better than FICON
■ buys you flexibility at the cost of complexity
■ tooling available, receiving better integration



More Information

I/O Connectivity on IBM zSeries mainframe servers
www.ibm.com/systems/z/connectivity/
Linux on zSeries: Fibre Channel Protocol Implementation Guide
www.redbooks.ibm.com/redpapers/pdfs/redp0205.pdf
How to use FC-attached SCSI devices with Linux on System z
download.boulder.ibm.com/ibmdl/pub/software/dw/linux390/docu/l26cts00.pdf
Linux for IBM System z Device Drivers Book and other documentation
http://www.ibm.com/developerworks/linux/linux390/documentation_dev.html
SLES 11 SP2: Storage Administration Guide
http://www.novell.com/documentation/sles11
/stor_admin/?page=/documentation/sles11/stor_admin/data/bookinfo.html
Red Hat Enterprise Linux 6: Storage Administration Guide
http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administ



Questions?

Susanne Wintenberger Schönaicher Strasse 220
71032 Böblingen, Germany
Certified IT Specialist Phone +49 (0)7031-16-3514
Linux on System z swinten@de.ibm.com


SCSI over FCP for Linux on System z

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