AIX Configuration Guide (Formerly Known as FAQ 1589)
This topic Includes:
Known Issues in AIX Configuration Guide
Overview
This guide provides configuration settings and considerations for Hosts running Advanced Interactive eXecutive (AIX) with SANsymphony.
Basic AIX storage administration skills are assumed including how to connect to iSCSI and Fibre Channel target ports and the discovering, mounting, and formatting of disk devices.
Change Summary
Changes since October 2019
| Section(s) | Content Changes |
|---|---|
| General Updates | This document has been reviewed for SANsymphony 10.0 PSP11. No additional settings or configurations are required. |
Refer to DataCore FAQ 838 for more information and see the Previous Changes that lists the earlier changes made to this document.
AIX Compatibility List
AIX Operating System Versions
Applies to all versions of SANsymphony 10.x.
| AIX | WITH AULA | WITHOUT AULA |
|---|---|---|
| 5.x | Not Supported | Not Supported |
| 6.1 | Not Supported | Not Supported |
| 7.1 | Not Supported | Qualified[1] |
| 7.2 | Not Qualified | Not Qualified[2] |
- Qualified vs Not Qualified vs Not Supported
- Refer to the Qualified vs Not Qualified vs Not Supported section for definitions.
- DataCore Server Port connections
- For AIX hosts, only Fibre Channel Front-end (FE) connections are supported.
- FE iSCSI connections are not supported.
- SCSI UNMAP
- There is no support for SCSI UNMAP from AIX hosts.
IBM PowerHA System Mirror (Formerly known as IBM PowerHA and HACMP)
Applies to all versions of SANsymphony 10.x. Refer to Qualified vs Not Qualified vs Not Supported for definitions.
| AIX | WITH AULA | WITHOUT AULA |
|---|---|---|
|
5.2 |
Not Supported | Not Supported |
|
5.3 |
Not Supported | Not Supported |
|
6.1 |
Not Supported | Not Supported |
|
7.1 |
Not Supported | Not Qualified |
|
7.2 |
Not Supported | Not Qualified |
Qualified vs Not Qualified vs Not Supported
Qualified
This combination has been tested by DataCore and all the host-specific settings listed in this document applied using non-mirrored, mirrored and dual virtual disks (vDisks).
Not Qualified
This combination has not yet been tested by DataCore using Mirrored or Dual vDisks types. DataCore cannot guarantee 'high availability' (failover/failback, continued access, etc.) even if the host-specific settings listed in this document are applied. Self-qualification may be possible.
Mirrored or dual vDisks types are configured at the user's risk; however, any problems that are encountered while using AIX versions that are 'Not Qualified' will still get root-cause analysis.
Non-mirrored vDisks are always considered 'Qualified' - even for 'Not Qualified' combinations of AIX/SANsymphony
Not Supported
This combination has either failed 'high availability' testing by DataCore using mirrored or dual vDisks types; or the operating System's requirements/limitations (e.g. age, specific hardware requirements) make it impractical to test. DataCore will not guarantee 'high availability' (failover/failback, continued access, etc.) if the host-specific settings listed in this document are applied. Mirrored or dual vDisks types are configured at the user's risk. Self-qualification is not possible.
Mirrored or dual vDisks types are configured at the user's risk; however, any problems that are encountered while using AIX versions that are 'Not Supported' will get best-effort DataCore Technical Support (e.g. to get access to vDisks) but no root-cause analysis will be done.
Non-mirrored vDisks are always considered 'Qualified' - even for 'Not Supported' combinations of AIX/SANsymphony
AIX versions that are End of Service
Self-qualification may be possible for versions that are considered ‘Not Qualified’ by DataCore but only if there is an agreed ‘support contract’ with IBM. Contact DataCore Technical Support before attempting any self-qualification of AIX versions that are End of Service (EOS).
For any problems that are encountered while using AIX versions that are EOS with DataCore Software, only best-effort DataCore Technical Support will be performed (e.g. to get access to vDisks). Root-cause analysis will not be done.
Non-mirrored vDisks are always considered 'Qualified'.
DataCore Server Settings
Operating System Type
When registering the host, choose one of the appropriate options:
- AIX 5.2 with ML9 or earlier chose ‘IBM AIX Native MPIO Legacy’
- AIX 5.2 with TL10 choose ‘IBM AIX’
- AIX 5.3 with ML5 or earlier chose ‘IBM AIX Native MPIO Legacy’
- AIX 5.3 with TL6 or greater choose ‘IBM AIX’
- AIX 6.1 and AIX 7.x choose ‘IBM AIX’
Port Roles
Ports that are used to serve virtual disks (vDisks) to hosts should only have the Front-end (FE) role checked. While it is technically possible to check additional roles on an FE port (i.e., Mirror and Backend), this may cause unexpected results after stopping the SANsymphony software.
Any port with FE role (and is serving vDisks to hosts) also has either the mirror and/or backend role enabled will remain ‘active’ even when the SANsymphony software is stopped. There is some slight difference in behavior depending on the version of SANsymphony installed.
SANsymphony 10.0 PSP7 and earlier
Any port that has the mirror and/or back-end role checked will remain ‘active’ after the SANsymphony software has been stopped.
SANsymphony 10.0 PSP8 and later
Only ports with the back-end role checked will remain ‘active’ after the SANsymphony software has been stopped.
FE ports that are serving vDisks but remain active after the SANsymphony software has been stopped can cause unexpected results for some host operating systems as they continue to try to access vDisks from the ‘active’ port on the now-stopped DataCore Server. This, in turn, may end up delaying host fail-over or result in complete loss of access from the host’s application/virtual machines (VM).
Multipathing
The Multipathing Support option should be enabled so that mirrored vDisks or dual vDisks can be served to hosts from all available DataCore FE ports. Refer to the Multipathing Support documentation for more information.
Non-mirrored vDisks and multipathing
Non-mirrored vDisks can still be served to multiple hosts and/or multiple host ports from one or more DataCore Server FE Ports if required; in this case, the host can use its own multipathing software to manage the multiple host paths to the single vDisk as if it was a mirrored or dual vDisk.
ALUA Support
Refer to AIX Compatibility List for more information.
Serving Virtual Disks
Serve a ‘LUN 0’ virtual disk to all hosts first
AIX’s MPIO uses the ‘LUN 0’ disk device on each port to be able to discover new disk devices that are served to the same port on an AIX Host. DataCore recommend to create one small, non-mirrored, virtual disk (vDisk)– on each DataCore Server in the Server Group - just for this purpose to make managing the serving of new virtual disks more convenient.
- Create one, ‘Single’ (i.e. non-mirrored) vDisk on each DataCore Server in the server group. The size of the vDisk should be as small as possible - i.e. the size of a single disk pool storage allocation unit (SAU).
- Serve each of these vDisks to all AIX host ports and ensure that the paths for these vDisks are configured as LUN 0.
Here is an example of one of these vDisks created on and served from DATACORE1 to both AIX Host 1 and AIX Host 2 as LUN 0 on each of their own Fibre Channel (FC) Ports.
- Make sure that each host discovers the vDisk on each of its ports from each of the DataCore Servers. There is no need to format this vDisk on the AIX Host as AIX’s MPIO is only using the disk device for discovering new LUNs on the port.
- Do not mirror the LUN 0 Virtual Disk
As no data is stored on this disk device there is no need to mirror the vDisk and it also avoids situations when the DataCore Server’s remote, mirror partner sets the vDisk as 'unavailable' to the AIX Host while the mirror is broken/in recovery. This prevents access to this LUN 0 and so stops (re)discovery of LUNs already served to the same host port.
- All other vDisks
DataCore recommends that before serving vDisks for the first time to a host, all DataCore FE ports on all DataCore Servers are correctly discovered by the host first.
Then, from within the SANsymphony Console, the vDisk is marked Online, up to date and that the storage sources have a host access status of Read/Write.
- To more than one Host port
DataCore vDisks always have their own unique Network Address Authority (NAA) identifier that a Host can use to manage the same vDisk being served to multiple ports on the same host server and the same vDisk being served to multiple Hosts.
While DataCore cannot guarantee that a disk device's NAA is used by a host's operating system to identify a disk device served to it over different paths generally we have found that it is. Additionally, while there is sometimes a convention that all paths by the same disk device always using the same LUN 'number' guarantees consistency for device identification, this may not be technically true. Always refer to the Host Operating System vendor’s documentation for advice on this.
DataCore's Software does, however always try to create mappings between the host's ports and the DataCore Server's FE ports for a vDisk using the same LUN number where it can. The software will first find the next available (lowest) LUN 'number' for the Host- DataCore FE mapping combination being applied and will then try to apply that same LUN number for all other mappings that are being attempted when the vDisk is being served. If any Host-DataCore FE port combination being requested at that moment is already using that same LUN number (e.g. if a host has other vDisks served to it from previous) then the software will find the next available LUN number and apply that to those specific Host-DataCore FE mappings only.
AIX Host Settings
DataCore Support for AIX MPIO Software
Download and install the DataCore Support for AIX MPIO software package on the AIX Host. For installation and configuration instructions, visit DataCore Support.
Disk Timeouts
rw_timeout and hcheck_interval settings
Set the ‘rw_timeout’ to 60 seconds and the ‘hcheck_interval’ to something equal to or higher than the ‘rw_timeout’ setting - as per IBM’s own recommendations.
Use the following command to change both the ‘hcheck_interval’ and ‘rw_timeout’ values at the same time:
A reboot of the Host is required to make these settings permanent.
Enable Fast I/O Failure
Use the following command to enable Fast I/O Failure for all Fibre Channel (FC) devices:
Device Queue Depth
Set the Device Queue Depth for all served DataCore virtual disks (vDisks).
- Identify the DataCore vDisk.
The following example shows 'hdisk2' as the DataCore vDisk.
- Get the disk device's attributes.
In the example above, the queue depth value is 1.
- Set the value to 16.
- Verify the change.
16 is the value that DataCore use when qualifying AIX. Larger values are possible up to and including 32. Larger values are not supported. Smaller values are also possible but may reduce Host performance for DataCore vDisks.
Known Issues in AIX Configuration Guide
The following is intended to make DataCore Software users aware of any issues that affect performance, access or may give unexpected results under particular conditions when SANsymphony is used in configurations with AIX Hosts.
These known issues may have been found during DataCore’s own testing but others may have been reported by our users when a solution was found that was not to do with DataCore’s own products.
DataCore cannot be held responsible for incorrect information regarding another vendor’s products and no assumptions should be made that DataCore has any communication with these other vendors regarding the issues listed here.
We always recommend that the vendor’s should be contacted directly for more information on anything listed in this section.
For ‘Known issues’ that apply to DataCore Software’s own products, please refer to the relevant DataCore Software Component’s release notes.
AIX may set the device queue depth to 1 for all DataCore virtual disks
It has been found in testing that disks served to AIX Hosts that are not detected as ‘IBM storage’ can have the queue depth to the minimum value of 1 which will significantly reduce host performance for DataCore virtual disks (vDisks). DataCore recommend a value of 16. Refer to the Device Queue Depth for instructions on how to change the queue depth setting on served DataCore vDisks.
Appendices
A: Preferred Server and Preferred Path Settings
Without ALUA Enabled
If hosts are registered without ALUA support, the Preferred Server and Preferred Path settings will serve no function. All DataCore Servers and their respective Front-end (FE) paths are considered ‘equal’.
It is up to the Host’s Operating System or Failover Software to determine which DataCore Server is its preferred server.
With ALUA Enabled
ALUA is not supported for AIX Hosts.
Refer to Preferred Servers and Preferred Paths for more information.
B: Reclaiming Storage from Disk Pools
How Much Storage will be Reclaimed?
This is impossible to predict.
SANsymphony can only reclaim Storage Allocation Units (SAU) that have no block-level data on them. If a host writes its data ‘all over’ its own filesystem, rather than contiguously, the amount of storage that can be reclaimed may be significantly less than expected.
Defragmenting Data on Virtual Disks
It may be possible to use a host’s defragmentation tools to consolidate data spread out all over the host’s filesystem but care should be taken as even more storage may be allocated while the existing data is defragmented.
Once any defragmentation is completed then additional steps will need to wipe the ‘free’ filesystem space on the host and then use SANsymphony’s ‘Manual Reclamation’ feature.
Notes on SANsymphony's Reclamation Feature
Automatic Reclamation
SANsymphony checks for any ‘zero’ write I/O as it is received by the disk pool and keeps track of which block addresses they were sent to. When all the blocks of an allocated SAU have received ‘zero’ write I/O, the storage used by the SAU is then reclaimed.
Mirrored and replicated virtual disks (vDisks) will mirror/replicate the ‘zero’ write I/O so that storage can be reclaimed on the mirror/replication destination DataCore Server in the same way.
Manual Reclamation
SANsymphony checks for ‘zero’ block data by sending read I/O to the storage. When all the blocks of an allocated SAU are detected as having ‘zero’ data on them, the storage used by the SAU is then reclaimed.
Mirrored vDisks will receive the manual reclamation ‘request’ on all DataCore Servers involved in the mirror configuration at the same time and each DataCore Server will read from its own storage.
The Manual reclamation ‘request’ is not sent to replication destination DataCore Servers from the source. Replication destinations will need to be manually reclaimed separately.
Reclaiming Storage on the Host Manually
A suggestion would be to create a ‘sparse file’ of an appropriate size and write zeroes it using the ‘dd’ command.
Here is an example with a 2TB sparse file:
Previous Changes
| Section(s) | Content Changes | Date |
|---|---|---|
| General Updates | This document has been reviewed for SANsymphony 10.0 PSP9. No additional settings or configurations are required. | October 2019 |
| The DataCore Server Settings – Port Roles |
Updated the content. |
July 2019 |
| General Updates |
Removed the following: All information regarding SANsymphony-V 9.x as this version is end of life (EOL). Refer to End of life notifications for DataCore Software products for more information. |
|
| AIX Compatibility List |
Updated the following: The minimum requirements have been amended (with footnotes) to allow for certain combinations of Service Pack + Technology Level that IBM now consider End of Service Pack Support. |
June 2019 |
| General Updates |
Updated the following: This document has been reviewed for SANsymphony 10.0 PSP8. No additional settings or configurations are required |
October 2018 |
| The AIX Host Settings |
Added the following: Operating System Settings Set the path health check interval (hcheck_interval). IBM’s own recommendation is that this should always be equal to or higher than the rw_timeout setting. Refer to the Path Health Check Settings section from IBM Developer Article for more information. Use the following chdev command to change both the hcheck_interval and rw_timeout value to appropriate values: chdev -l hdiskX -a hcheck_interval=90 –a rw_timeout=60 -P
Where ‘hdiskX’ is the number of the DataCore virtual disk device as discovered on the AIX Host. A reboot will be required to make the settings permanent over any future reboots of the AIX Host. Enable Fast I/O Failure for Fibre Channel (FC) devices Use the following chdev command to enable Fast I/O Failure for Fibre Channel (FC) devices: chdev -l fscsiX -a dyntrk=yes -a fc_err_recov=fast_fail -P
Where ‘fscsiX’ is the number of the AIX Host’s FC device. Refer to Fast I/O Failure for Fibre Channel devices for more information. |
May 2018 |
| General Updates |
Updated the following: This document has been reviewed for SANsymphony 10.0 PSP7. No additional settings or configurations are required. |
February 2018 |
|
Removed the following: Appendix B – Configuring Disk Pools The information here has been removed as it is now superseded by the information in: DataCore Server- Best Practice Guidelines. What was previously 'Appendix C' has now been moved to 'Appendix B'. |
||
| AIX Compatibility List |
Added the following: A note has been added regarding the qualification status of IBM PowerHA SystemMirror (formerly known as IBM PowerHA and HACMP). |
August 2017 |
| General Updates |
Updated the following: This document has been reviewed for SANsymphony 10.0 PSP 6 update 4. No additional settings or configurations are required. |
April 2017 |
| Appendix C - Reclaiming storage |
Updated the following: Automatic and Manual reclamation These two sections have been re-written with more detailed explanations and technical notes. |
November 2016 |
| Known Issues |
AIX can set the Device Queue Depth to 1 for DataCorevDisks The example showed how to set, using the chdev command, the queue_depth parameter for an hdisk to '16' and the footnote for the example merely stated that values larger than 32 should not be used, without any context. The footnote now reads: "'16' is the value that DataCore use when qualifying AIX. Larger values are possible but any that are greater than '32' are not supported by DataCore. Smaller values can also be used instead, if preferred. Refer to the IBM's documentation for more information. |
August 2016 |
| General Updates |
Updated the following: This document has been reviewed for SANsymphony 10.0 PSP 5. No additional updates were required. |
July 2016 |
|
Added the following: AIX compatibility lists AIX Version 7.2 |
||
| General Updates |
Added the following: A new section: 'Known Issues' The information added was previously documented in DataCore Support's FAQ 981.
|
December 2015 |
| General Updates |
SANsymphony -V 8.x and all versions of SANsymphony 9.x before 10.0 PSP4 Update 4 are now ‘End of Life’. Refer to End of Life Notifications for more information. |
November 2015 |
| List of qualified AIX Versions - Notes on qualification |
Added the following: This section has been updated and new information added regarding the definitions of all ‘qualified’, ‘unqualified’ and ‘not supported…’ labels. A new section on AIX versions that are no longer in development has also been added at the end of this section. |
June 2015 |
| List of qualified AIX Versions |
Updated the following: AIX 7.1 is now qualified with SANsymphony-V 10.x using non-ALUA settings. ISCSI is still not considered qualified at this time; all qualified versions are with Fibre Channel only. |
February 2015 |
| 2014 and earlier | ||
| Technical Bulletin Compilation |
No new technical information has been added but this document now combines all of DataCore’s AIX-related information from older Technical Bulletins into a single document including: Technical Bulletin 6: “AIX Hosts” Technical Bulletin 8: “Formatting Host’s File Systems on Virtual Disks created from Disk Pools” Technical Bulletin 11: “Disk Timeout Settings on Hosts” Technical Bulletin 16: “Reclaiming Space in Disk Pools” |
December 2014 |
| Qualified Distributors |
Added the following: Which Distributions are qualified? Added new tables to show which versions are explicitly qualified, unqualified and not supported with either SANsymphony-V 8.1 PSP1 Update 4, 9.x and 10.x, and if the configuration is with or without ALUA enabled Hosts. Note that the minimum requirement for SANsymphony-V 8.x is now 8.1 PSP1 Update 4 |
|
| Appendix |
Appendix A This section gives more detail on the Preferred Server and Preferred Path settings with regard to how it may affect a Host. |
|
|
Appendix B This section incorporates information regarding “Reclaiming Space in Disk Pools” (from Technical Bulletin 16) that is specific to AIX Hosts. |
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| Host Settings |
Updated the following: Host Settings - Improved explanations to most of the required Host Settings and DataCore Server Settings generally. Technical Bulletin 6: “AIX Hosts” |
|
| General Updates | Removed all references to SANmelody as this is now ‘End of Life’ of December 31 2012. Removed all references to iSCSI as this is not supported with AIX. | April 2013 |
| General Updates | Updated for SANsymphony-V 9.x. No new technical information. | July 2012 |
| DataCore Server and Host minimum requirements | Updated DataCore Server and Host minimum requirements. Removed all references to ‘End of Life’ SANsymphony and SANmelody versions that are no longer supported as of December 31 2011. | January 2012 |
| General Updates | Removed all references to ‘End of Life’ SANsymphony and SANmelody versions that are no longer supported as of July 31 2011. | November 2011 |
| General Updates | Added SANsymphony-V 8.x | October 2011 |
| General Updates | Added AIX 7.1 | June 2011 |
| General Updates | Added AIX 6.1.x | July 2009 |
| First publication of document |
Initial publication of Technical Bulletin. Added AIX 5.2 TL10 |
March 2009 |