Troubleshooting
Problem
Sometimes sissasraidmgr will indicate a status of *unKnwn* and missing for
a SAS disk and its associated pdisk.
a SAS disk and its associated pdisk.
Symptom
Example:
********** RAID Configuration *************
------------------------------------------------------------------------
Name Resource State Description Size
------------------------------------------------------------------------
sissas0 FEFFFFFF Available PCIe3 x8 SAS RAID Internal Adapter 6Gb
------------------------------------------------------------------------
Name Resource State Description Size
------------------------------------------------------------------------
sissas0 FEFFFFFF Available PCIe3 x8 SAS RAID Internal Adapter 6Gb
hdisk1 FC0200FF Optimal 4K RAID 0 Array 283.9GB
pdisk1 0003FFFF Active 4K Array Member 283.9GB
pdisk1 0003FFFF Active 4K Array Member 283.9GB
*unknwn* 0002FFFF Unknown 4K Array Candidate N/A
pdisk0 0002FFFF Missing Disk 283.9GB
pdisk0 0002FFFF Missing Disk 283.9GB
********** Multi-path Summary *************
pdisk0 Path 1: Operational
pdisk1 Path 1: Operational
ses0 Path 1: Operational
pdisk1 Path 1: Operational
ses0 Path 1: Operational
In this example we see pdisk0 shows "Missing" and its associated hdisk
shows *unknwn*
Cause
The adapter firmware keeps a table of all SAS disks. The 'unKnwn' and missing entries in the SAS raid manager (sissasraidmgr) output are usually a sign that the adapter firmware has discovered a device which wasn't present the last time the adapter scanned for new SAS devices.
We see this when required host-side steps were missed during a SAS disk replacement. To ensure that the firmware is in a consistent state, we need to eithr run diagnostics on the adapter to correct the information presented, or reboot the system to force the adapter to do a full scan of SAS devices.
We see this when required host-side steps were missed during a SAS disk replacement. To ensure that the firmware is in a consistent state, we need to eithr run diagnostics on the adapter to correct the information presented, or reboot the system to force the adapter to do a full scan of SAS devices.
Resolving The Problem
First remove the Missing devices from the ODM first. For each "missing" hdisk (if any),
by running the commands below as root:
#rmdev -dl hdisk# (notice it's the hdisk - not the pdisk!) (replace the # with hdisk number)
#cfgmgr
Then check the status of the disk on the SAS adapter by the following command:
#sissasraidmgr -L -l sissas# -j3 (replace the # with sissas number)
by running the commands below as root:
#rmdev -dl hdisk# (notice it's the hdisk - not the pdisk!) (replace the # with hdisk number)
#cfgmgr
Then check the status of the disk on the SAS adapter by the following command:
#sissasraidmgr -L -l sissas# -j3 (replace the # with sissas number)
If the issue still exists after the above steps, run diagnostics in system verification mode on the adapter to reset the adapter and rediscover the devices and connections. This can be done while the system is up:
1-diag
2-Advanced Diagnostics Routines
3-System Verification
4-[select the adapter to test - Example: sissas0 ]
5-[press F7 to run]
6-[press Enter]
7-[You can answer NO to the Service Focal Point question]
8-[Press F10 to exit the diag program]
Once you have completed the above diagnostics from the adapter, run the commands below to see the status of the disk:
#sissasraidmgr -L -l sissas0 -j3
If that fails to correct the missing/unknwn entries, reboot the system.
After reboot, sissasraidmgr should indicate that an Active Array Candidate has now been configured and has a known pdisk device name.
After reboot, sissasraidmgr should indicate that an Active Array Candidate has now been configured and has a known pdisk device name.
The next steps are to prepare the pdisk to use in a RAID 0 array by following these menu steps in smitty sasdam:
1-smitty sasdam
2-Create an Array Candidate pdisk and format it to a RAID block size
3-Select the controller from the list
4-Select the new drive to be formatted as an Array Candidate
5-The status bar will show the formatting progress
1-smitty sasdam
2-Create an Array Candidate pdisk and format it to a RAID block size
3-Select the controller from the list
4-Select the new drive to be formatted as an Array Candidate
5-The status bar will show the formatting progress
After the above steps, create a SAS Disk Array candidate on the formatted disk, as shown below:
1-smitty sasdam
2-Create a SAS Disk Array
3-Select the sissas# adapter and press Enter (replace the # with sissas number)
4-Select RAID level 0 and press Enter
5-Select 256Kb and press Enter
6-Select the new pdisk and press Enter
7-Review settings and press Enter to create the array
Once the array creation is complete, a new hdisk should be configured and available for use.
1-smitty sasdam
2-Create a SAS Disk Array
3-Select the sissas# adapter and press Enter (replace the # with sissas number)
4-Select RAID level 0 and press Enter
5-Select 256Kb and press Enter
6-Select the new pdisk and press Enter
7-Review settings and press Enter to create the array
Once the array creation is complete, a new hdisk should be configured and available for use.
Related Information
IBM Power System SAS or SSD disk replacement in AIX or VIOS
How to replace a failed SAS disk (pdisk) in a RAID 0 array
Replacing a SAS RAID (0) Array drive that is part of rootvg in VIOS environment
How to Replace Failing Disk in VIOS, Mirrored Rootvg
RAID configuration on the IBM Power platform
Document Location
Worldwide
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Document Information
Modified date:
03 October 2025
UID
ibm17246682