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What’s New With AIX in 2020

AIX expert Jaqui Lynch breaks down the latest updates for the OS.

2020 in white text surrounded by fading circles on a blue background.

AIX version 7 has been around for a long time now, so it’s time to look into some of the more recent updates that have come out with AIX 7.2 that may be useful in your data centers. Below we look into some of the updates that I have found to be interesting as I review them.

Multipath I/O

Starting with AIX 7.2 tl3, AIX now provides MPIO support for parallel SCSI, iSCSI and Fiber channel devices. MPIO is integrated into AIX with the AIXPCM drivers.  SDDPCM is not supported on POWER9 servers. IBM also announced that SDDPCM will not be supported in Spectrum Virtualize after 8.3.0. It’s also not supported on the SVC or Storwize hardware from machine code v7.6.1. No new fixes will be provided to SDDPCM at any level after June 30, 2020. This means it’s time to migrate from SDDPCM to AIXPCM. 
AIXPCM provides path management functions and health checks. The health checks allow AIXPCM to check the paths and determine which paths are usable for sending I/O, enable failed paths once they are returned to service and to check for unused paths that would be used if a failover occurred. It also removes many of the issues with upgrading OSes where the LPAR is booted from the SAN with SDDPCM drivers. With AIXPCM, there are two types of attributes that you need to review - device attributes and path attributes. The defaults are not necessarily what you would normally run with.  There is an excellent writeup on all of these in the AIX modernization Redbook from IBM. Key parameters to review are:
algorithm = fail_over or round_robin or shortest_queue

The above impact how the I/O will be distributed across the paths. The default is fail_over which means the path with the highest priority will be chosen and other paths are only used if this one fails. round_robin distributes I/O across all the enabled paths depending on priority and whether paths are set to preferred or not. shortest_queue selects paths based on the length of the queue for that path. You can see these settings as follows:

lsattr -El hdisk4 | grep algo

algorithm       round_robin                                        Algorithm                    True+

You should also check the settings for hcheck_mode and reserve_policy:

 lsattr -El hdisk4 | grep hcheck

hcheck_mode     nonactive                                        Health Check Mode    True+

hcheck_mode=nonactive means the healthcheck command is sent to all paths that do not have any active I/O. This includes paths that are in enabled and failed states. This is the default.

Other modes include enabled which sends the command to only enabled and failed paths, or failed which only sends the command to failed paths.

lsattr -El hdisk4 | grep reserve

reserve_policy  no_reserve                                         Reserve Policy          True+ 

The default reserve_policy is single_path. This policy uses SCSI2 reserves and will cause problems in a PowerHA or an LPM environment. reserve_policy should be set to no_reserve in these environments where disks are shared between hosts. It also should be set if devices have the shortest_queue or round_robin algorithms configured.

lsattr -El hdisk4 | grep queue

queue_depth     20                                                        Queue DEPTH         True+

queue_depth controls the number of concurrent commands that AIX can senf to the device concurrently. This should be set according to performance needs and disk vendor recommendations.

You can check path status for an hdisk as follows—this shows all the paths for that disk and whether they are optimized (opt), selected for the I/O when lsmpio was run (sel) or non optimized (non)

lsmpio -l hdisk4 

name    path_id status   path_status  parent connection

hdisk4  0       Enabled  Non          fscsi0  500507680d048ef6,6000000000000

hdisk4  1       Enabled  Sel,Opt      fscsi0 500507680d048ef7,6000000000000

hdisk4  2       Enabled  Non          fscsi1  500507680d088ef6,6000000000000

hdisk4  3       Enabled  Sel,Opt      fscsi1 500507680d088ef7,6000000000000

More detailed information on the disk can be found as follows:

lsmpio -ql hdisk4

Device:  hdisk4

          Vendor Id:  IBM

         Product Id:  2145

           Revision:  0000

           Capacity:  200.00GiB

       Machine Type:  2078

       Model Number:  124

         Host Group:  P8NIM

        Volume Name:  NIM_200GB_nimvg3

      Volume Serial:  60050763808100F70000000000000026  (Page 83 NAA) 

This provides the serial number, the name in the disk subsystem for the LUN, the size and the machine type and model for the disk subsystem.


You can also find the parent for an hdisk and get statistics on each of the paths using:

lsmpio -are -l hdisk4

This will show a long report that includes all the paths. An example of part of one of those reports is below:

Adapter Driver: fscsi0 -> AIX PCM

    Adapter WWPN:  c0507607dbd80028

    Link State:    Up

    Connection Errors

    Last 10 Minutes:                          0

    Last 60 Minutes:                          0

    Last 24 Hours:                            0

A more indepth set of statistics for the hdisk is available using the “lsmpio -l hdisk4 -S” command. More details are available if you add the -d flag “lsmpio -l hdisk4 -Sd”.

Additionally, lspath was updated with new –t and –i flags. The –t flag ensures the pathid is listed at the end, and the –i flag allows you to specify the pathid and only get information for devices on that specific path. The mkpath and rmpath commands were also updated to include the option to process specific pathids.

lspath -t -l  hdisk4

Enabled hdisk4 fscsi0 0

Enabled hdisk4 fscsi0 1

Enabled hdisk4 fscsi1 2

Enabled hdisk4 fscsi1 3

You can then narrow it down to only look at path 0 for the disk:

lspath -l hdisk4 -I 0

Enabled hdisk4 fscsi0

Or you can ask the system to report on all hdisks connected to path 0, which is useful if you have to take a path offline:

lspath -i 0

Enabled hdisk4  fscsi0

Enabled hdisk0  fscsi0

Enabled hdisk1  fscsi0

Enabled hdisk2  fscsi0

Enabled hdisk3  fscsi0

Enabled hdisk5  fscsi0

Enabled hdisk6  fscsi0

Enabled hdisk7  fscsi0

Enabled hdisk8  fscsi0

Enabled hdisk9  fscsi0

Enabled hdisk10 fscsi0

If the default settings for options such as reserve_policy are not acceptable you can change the default for devices so that new devices are always created with the setting you prefer. An example would be:

 chdef -t mpioosdisk -c disk -s fcp -a reserve_policy=no_reserve

The above changes the default reserve_policy for new disks. It is recommended that you run bosbootafter changing the default. You can check for all attributes that have been changed from defaults using “chdef -H”.

Additionally, paths can have their priorities changed, or be enabled or disabled using the chpath command.

It should be noted that when migrating from SDDPCM to AIXPCM all the values that you may have changed on devices will be reset to system defaults. It’s important that you reset these after the migration.

iSCSI Support 

As of AIX 7.2 TL 3 and above, AIX now has native support for using AIX as an iSCSI initiator by using any network adapter. After updating to AIX 7.2 TL3, there is a new device that is labeled iscsi0 on your AIX system. This device is the iSCSI Protocol Device, and it is the parent adapter for all your iSCSI targets. It also holds the configuration attributes for your iSCSI software initiator. These values can be updated either by using smitty or by running the fast path smitty chgiscsisw. Settings can be checked using the lsdev and lsattr commands.

lsdev -C | grep iscsi

iscsi0         Available             iSCSI Protocol Device


lsattr -El iscsi0

disc_filename  /etc/iscsi/targets      Configuration file  

disc_policy    file                              Discovery Policy  

immediate_data no                         Support ImmediateData 

initial_r2t    yes                                Require InitialR2T          

initiator_name iqn.localhost.hostid.7f000001 iSCSI Initiator Name   

isns_srvnames  auto                        iSNS Servers IP Addresses 

isns_srvports                                   iSNS Servers Port Numbers 

isw_err_recov  delayed_fail             iSCSI Network Error Recovery Policy 

max_targets    16                             Maximum Targets Allowed    

max_xfer_size  0x80000                  Maximum transfer 

num_cmd_elems  200                      Maximum number of commands to queue to driver

NIM Improvements 

A large number of improvements have been made to NIM since it was first developed. Since AIX 7.2 there have been multiple features added to support new OS functions.

In order to support live update, a new management object class was added. This requires that you install dsm.core, but it then provides new object types thatinclude nas_filer, hmc, cec, vios, ivm, bcmm (blade center management module) and PowerVC. This allows NIM to define and manage these control points. Live update specifically requires the definition of the HMC and CEC objects as well as an object for the LPAR and a new live update object. The new control points become available for configuration when dsm.core is installed.

The use of these new objects allows you to set up associatiojs from the HMC to the CEC to the AIX LPAR so that you can perform operations such as live update which require authentication. There is a new “dpasswd” command to set up the authentication component.

In AIX 7.2 NIM now has a new service handler that provides HTTP access to NIM resources called nimhttp. The nimhttp service is defined in /etc/services, and the nimhttp daemon listens for requests over port 4901. 

If nimhttp is configured and active then NIM clients can access some resources using the http service on port 4901 (or a port specified on /etc/services).

grep nimhttp /etc/services

nimhttp        4901/tcp

nimhttp        4901/udp


NIM resources that support HTTP access include:

·     file_res

·     fix_bundle

·     installp_bundle

·     lpp_source

·     script

nimhttp is enabled using the nimconfig -h command which is not covered in the man page.

Cloning Updates

In my system maintenance I make extensive use of AIX clones, specifically with alt_disk_copy. I also occasionally use alt_disk_mksysb to create an alternate image from a mksysb image. There are times when I want to have more than one copy out there but you can only have one altinst_rootvg volume group at a time. This means it is necessary to rename the one you want to keep. This is done with alt_rootvg_op

alt_rootvg_op -v rootvg1220 -d hdisk1

This renames altinst_rootvg on hdisk1 to be rootvg1220 and I can now create a second clone on another hdisk. If you need to perform operations on the clone after it is created, you can access it using:

 alt_rootvg_op -W -d hdisk1

 Next, put it back to sleep after making the changes using:

alt_rootvg_op -S -d hdisk1

These are useful commands to remember if you have to update something like /etc/hosts after the clone is taken.

 AIX Toolbox for Linux

IBM has now moved to using yum to install third-party products such as samba or gcc that IBM provides using the AIX Linux Toolbox. This makes it far easier to install these products and ensure dependencies are being met. YUM is installed by running the found on the AIX Toolbox for Linux website and more information is provided in the yum readme on how to install and use YUM. If you have previously installed toolbox products outside the toolbox and yum then you may have some cleanup work to do prior to getting YUM to install.

SMT Defaults

With POWER9 and AIX 7.2 tl3 IBM has changed the default for SMT from SMT4 to SMT8. This now allows a maximum of 1536 threads for an LPAR. 

AIX and PowerVM Secure Boot and POWER9 Firmware 940

Secure boot was introduced to AIX in 7.2 tl3 (also PowerVM v3).  POWER9 hardware and firmware include new PowerVM features to support Secure boot. This allows only appropriately signed firmware components to run on the system processors. Each component of the firmware stack, including HostBoot, the IBM POWER Hypervisor (PHYP), and the Partition Firmware (PFW) is signed by the platform manufacturer and verified as part of the IPL process. AIX Secure Boot extends this to the AIX LPAR. 

POWER9 firmware level 940 has code in it that supports Secure Boot at the firmware level. There’s a warning in the readme that this requires your HMC to be at HMC v9R1M940 and that any boot capable PCI adapters must be updated to the latest firmware prior to upgrading to firmware 940 as the more recent levels include signed boot driver code. The LPAR will still boot if the adapter is not updated but will produce multiple error entries for BA5400A5 and BA5400A6.

There are also specific warnings that Novalink with certain SRIOV capable adapters is not supported at POWER9 firmware 930 or 940.

PowerVM v3.1

PowerVM v3.1 is the AIX 7.2 tl3 and higher version of the VIO server. The installation takes place using alt_disk_copy and requires a second disk to install to. It is a complete rootvg replacement so you will need to do any customizations again after the system has rebooted at the new level. Your virtual definitions will be backed up and restored but any changes you have made to logging, /etc/hosts or other rootvg files will need to be redone. You can tell the upgrade to save certain files for you in /home/padmin so you can restore the information later if you need to.

This version adds support for iSCSI over vSCSI and it also supports iSCSI MPIO. Additionally, it provides updates for NPIV. The 16GB adapters still have a maximum of 64 active VFCs but the 32GB adapters can now support 255 active VFCs.

Updates to LPM (Live Partition Mobility)

The default compatibility mode on POWER9 has been POWER9-base. After firmware 940 is installed there is a new mode added called POWER9. LPARss running in POWER9 compatibility mode are only supported on POWER9 servers running firmware 940. If you plan to LPM between POWER9 servers at different firmware levels make sure they are set to POWER9-base as a mode.

HMC v9r1m930 and POWER9 now allow for bidirectional concurrent migrations. Prior to these levels, migrations could only go in one direction at a time.

As of HMC v9r1m920 it’s possible to use LPM to migrate LPARs between servers that have the same serial number although they must be different machine types and models. Each machine must be on a different HMC as well.  This allows you to use LPM to migrate LPARs to a new server when using the same serial number as part of an upgrade; e.g., when upgrading from an E880 to an E980 using serial number protection.

General Updates

You can monitor the frequency your system is running at in several ways. Options include mpstat, lparstat and nmon. With nmon in logging mode you add “-y dfreq=on” to the command line. If you are in interactive mode you can use the R flag and then look for the CPU-Current-Speed:

 CPU-Current-Speed 2047.1 MHz

mpstat -E 1 1


System configuration: lcpu=8 ent=0.5 mode=Uncapped

 vcpu          pbusy           physc           freq            scaled physc

 ----          -----           -----           ----            ------------

   0       0.0018[  0%]       0.0101[  2%]     2.0GHz[ 55%]   0.0056[ 1%]

   4       0.0001[  0%]       0.0003[  0%]     2.8GHz[ 75%]   0.0002[ 0%]

 ALL       0.0019[  0%]       0.0103[  2%]     2.0GHz[ 55%]   0.0057[ 1%]



There are many updates beyond what I have shared in this article that have come out in AIX 7.2. Every technology level adds more to the mix. AIX 7.1 is now coming close to end of life. All levels of AIX 7.1 prior to tl05 went out of support by 12/31/2019. 7.1.5 will still be supported until 4/30/2023. AIX 7.2 has been around since 2015 and IBM is slowly ending support for older technology levels; 7.2.1 went out of support on Nov. 20, 2019  and tl02 goes out of support on Oct. 31, 2020. This is a good time to look at updating to the latest tl ( so that you are current, supported and can take advantage of all the new features that AIX has to offer. All PowerVM software prior to 2.2.6 also went out of support 9/30/2019 so this is also the time to update to PowerVM v3.1. I highly recommend reading the AIX Enhancements and Modernization Redbook so that you’re aware of all of the new features that are now available.


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