Question & Answer
Question
A system with a large number of disks and large number of paths seems to hang when trying to display a list of bootable devices in SMS boot utility screens.
Cause
When the SMS option of "List all devices" is selected, the firmware will open every available adapter, and probe for every SAN target device port. It will then probe every available LUN behind that target device port. Finally, each LUN is probed for a valid boot image. This process can take up to several seconds per detected LUN.
In the case of a system (standalone or VIOS partition) with a large number of disks, and multiple paths, this process may appear to be hung since all adapters and all detected devices are probed before a final list is displayed to the screen.
Answer
There are a couple of options to reduce the SMS scan time:
Option A - Reduce the number of paths
To reduce the number of paths during the first boot, you can disable all but one zone on the SAN switch. That zone should include only a single (virtual or physical) FC adapter and a single storage port WWPN. This should reduce the number of paths SMS needs to scan. Once the boot device is found, and the lpar is up and running again, you can add the other paths back by re-enabling the SAN zoning, and then running "cfgmgr" (AIX) or "cfgdev" (VIOS).
Option B - Specify the boot lun manually in SMS
Another alternative to changing the zoning would be to manually select the path and device in SMS. This assumes you know the WWPN of the storage port you intend to boot from, and the LUN ID that was assigned to the rootvg disk with the hd5 boot LV.
1) Boot into SMS.
2) Select "Select Boot Options".
3) Select "Configure Boot Device Order".
4) Select "Select 1st Boot Device"
5) Select "Hard Drive"
6) Select "SAN"
7) Select one of the virtual FC adapters.
8) Select "Specify a boot device using WWPN and LUN"
- Manually enter the port WWPN
- Manually enter the LUN ID
- Press ESC to return to previous menu
9) Select "Set Boot Sequence: Configure as 1st Boot Device"
(this may take a while to complete)
10) Once it's been selected, you can attempt the boot. However if it fails, you will need to use option A again.
Option A - Reduce the number of paths
To reduce the number of paths during the first boot, you can disable all but one zone on the SAN switch. That zone should include only a single (virtual or physical) FC adapter and a single storage port WWPN. This should reduce the number of paths SMS needs to scan. Once the boot device is found, and the lpar is up and running again, you can add the other paths back by re-enabling the SAN zoning, and then running "cfgmgr" (AIX) or "cfgdev" (VIOS).
Option B - Specify the boot lun manually in SMS
Another alternative to changing the zoning would be to manually select the path and device in SMS. This assumes you know the WWPN of the storage port you intend to boot from, and the LUN ID that was assigned to the rootvg disk with the hd5 boot LV.
1) Boot into SMS.
2) Select "Select Boot Options".
3) Select "Configure Boot Device Order".
4) Select "Select 1st Boot Device"
5) Select "Hard Drive"
6) Select "SAN"
7) Select one of the virtual FC adapters.
8) Select "Specify a boot device using WWPN and LUN"
- Manually enter the port WWPN
- Manually enter the LUN ID
- Press ESC to return to previous menu
9) Select "Set Boot Sequence: Configure as 1st Boot Device"
(this may take a while to complete)
10) Once it's been selected, you can attempt the boot. However if it fails, you will need to use option A again.
Power9, Power10: Additional functionality added to SMS menus that was once provided by the old info program.
Please refer to "I/O device information" at the following link :
https://www.ibm.com/docs/en/power9?topic=services-io-device-information
Follow the SMS menu examples shown to display WWPN/LUN and disk sizes as well as Inquiry Data (disk sizes and more) for each target device down each adapter.
That document covers the functionality that was previously provided by info command in earlier firmware releases that has been moved to SMS menus.
OLDER LEGACY SYSTEMS: (Power8, 7, 7+ machines ONLY)
In case you don't know ahead of time what is the storage port WWPN and LUN ID you can boot into open firmware and scan for disks one adapter at a time. This may still take a while depending on how many disks are configured, but it should be less time than the SMS scan of ALL devices, down ALL adapters.
1) Boot into Open Firmware (versus SMS) by pressing "8" during the boot "window of opportunity".
2) At the "0>" prompt, type in "ioinfo"
3) Select "FCINFO"
4) Select an adapter slot
5) Select "List Attached FC Devices"
This will show all the WWPN,LUN combinations, their disk size, and if it is bootable.
In case you don't know ahead of time what is the storage port WWPN and LUN ID you can boot into open firmware and scan for disks one adapter at a time. This may still take a while depending on how many disks are configured, but it should be less time than the SMS scan of ALL devices, down ALL adapters.
1) Boot into Open Firmware (versus SMS) by pressing "8" during the boot "window of opportunity".
2) At the "0>" prompt, type in "ioinfo"
3) Select "FCINFO"
4) Select an adapter slot
5) Select "List Attached FC Devices"
This will show all the WWPN,LUN combinations, their disk size, and if it is bootable.
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Document Information
Modified date:
12 December 2023
UID
isg3T1025143