Setting new device attributes with chdef
While building a new LPAR recently I stumbled across the chdef command. This command modifies the default value of a predefined attribute of the specified device type in the ODM (PdDv). For devices that are already configured and of the same class, subclass, and type, this command does not change the active devices attributes, instead it modifies the ODM attributes so these will be changed the next time you reboot the LPAR or rmdev and cfgmgr the device. The chdef command is a bit like using the chdev -P flag, except it changes the predefined values and the values currently configured for every device that matches the same class, subclass and type.
Let us take a look at the settings on a newly built LPAR and then make some changes with chdef.
Checking the default build settings for vscsi1.
lsattr -El vscsi1
rw_timeout 0 Virtual SCSI Read/Write Command Timeout True
vscsi_err_recov delayed_fail N/A True
vscsi_path_to 0 Virtual SCSI Path Timeout True
Checking the default build settings for vscsi2.
lsattr -El vscsi2
rw_timeout 0 Virtual SCSI Read/Write Command Timeout True
vscsi_err_recov delayed_fail N/A True
vscsi_path_to 0 Virtual SCSI Path Timeout True
Check the defaut build settings for hdisk0 (rootvg).
lsattr -El hdisk0
PCM PCM/friend/vscsi Path Control Module False
algorithm fail_over Algorithm True
hcheck_cmd test_unit_rdy Health Check Command True+
hcheck_interval 0 Health Check Interval True+
hcheck_mode nonactive Health Check Mode True+
max_transfer 0x40000 Maximum TRANSFER Size True
pvid 0012345678900000000000000000 Physical volume identifier False
queue_depth 3 Queue DEPTH True
reserve_policy no_reserve Reserve Policy True+
Find the Class, Subclass and Type values for vscsi adapters.
lsdev -H -F "name class subclass type" | grep -e ^name -e vscsi
name class subclass type
hdisk0 disk vscsi vdisk
vscsi1 adapter vdevice IBM,v-scsi
vscsi2 adapter vdevice IBM,v-scsi
Find the Class, Subclass and Type values for hdisks.
lsdev -H -F "name class subclass type" | grep -e ^name -e hdisk
name class subclass type
hdisk0 disk vscsi vdisk
Change the ODM settings for the vSCSI adapters.
Set the rw_timeout, vscsi_err_recov and vscsi_path_to options.
chdef -a rw_timeout=120 -c adapter -s vdevice -t IBM,v-scsi
chdef -a vscsi_err_recov=fast_fail -c adapter -s vdevice -t IBM,v-scsi
chdef -a vscsi_path_to=30 -c adapter -s vdevice -t IBM,v-scsi
Verify the settings have changed in the ODM.
lsattr -El vscsi1
rw_timeout 120 Virtual SCSI Read/Write Command Timeout True
vscsi_err_recov fast_fail N/A True
vscsi_path_to 30 Virtual SCSI Path Timeout True
lsattr -El vscsi2
rw_timeout 120 Virtual SCSI Read/Write Command Timeout True
vscsi_err_recov fast_fail N/A True
vscsi_path_to 30 Virtual SCSI Path Timeout True
Verify the running adapter has not changed.
lsattr -Pl vscsi1
rw_timeout 0 Virtual SCSI Read/Write Command Timeout True
vscsi_err_recov delayed_fail N/A True
vscsi_path_to 0 Virtual SCSI Path Timeout True
lsattr -El vscsi2
rw_timeout 0 Virtual SCSI Read/Write Command Timeout True
vscsi_err_recov delayed_fail N/A True
vscsi_path_to 0 Virtual SCSI Path Timeout True
Change the ODM settings for the vSCSI disks.
chdef -a hcheck_interval=120 -c disk -s vscsi -t vdisk
chdef -a hcheck_mode=nonactive -c disk -s vscsi -t vdisk
chdef -a queue_depth=16 -c disk -s vscsi -t vdisk
Verify the settings have changed in the ODM.
lsattr -El hdisk0
PCM PCM/friend/vscsi Path Control Module False
algorithm fail_over Algorithm True
hcheck_cmd test_unit_rdy Health Check Command True+
hcheck_interval 120 Health Check Interval True+
hcheck_mode nonactive Health Check Mode True+
max_transfer 0x40000 Maximum TRANSFER Size True
pvid 0012345678900000000000000000 Physical volume identifier False
queue_depth 16 Queue DEPTH True
reserve_policy no_reserve Reserve Policy True+
Verify the running hdisk has not changed.
lsattr -Pl hdisk0
PCM PCM/friend/vscsi Path Control Module False
algorithm fail_over Algorithm True
hcheck_cmd test_unit_rdy Health Check Command True+
hcheck_interval 0 Health Check Interval True+
hcheck_mode nonactive Health Check Mode True+
max_transfer 0x40000 Maximum TRANSFER Size True
pvid 0012345678900000000000000000 Physical volume identifier False
queue_depth 3 Queue DEPTH True
reserve_policy no_reserve Reserve Policy True+
To list all the default settings that have been changed with chdef.
I added the header line in for clarity.
chdef
Attribute New Default AIX Default Device Type
dyntrk yes yes driver/vionpiv/efscsi
fc_err_recov fast_fail fast_fail driver/vionpiv/efscsi
hcheck_cmd inquiry test_unit_rdy PCM/friend/vscsi
hcheck_interval 120 0 PCM/friend/vscsi
hcheck_mode nonactive nonactive PCM/friend/vscsi
rw_timeout 120 0 adapter/vdevice/IBM,v-scsi
vscsi_err_recov fast_fail delayed_fail adapter/vdevice/IBM,v-scsi
vscsi_path_to 30 0 adapter/vdevice/IBM,v-scsi
Adding a New vSCSI Device
Before the adding of the new device.
lsdev -Cc adapter | grep vscsi
vscsi1 Available Virtual SCSI Client Adapter
vscsi2 Available Virtual SCSI Client Adapter
From the HMC, I used DLPAR to add another vSCSI device.
cfgmgr
lsdev -Cc adapter | grep vscsi
vscsi0 Available Virtual SCSI Client Adapter
vscsi1 Available Virtual SCSI Client Adapter
vscsi2 Available Virtual SCSI Client Adapter
Confirm the new device has the updated settings in the ODM.
lsattr -El vscsi0
rw_timeout 120 Virtual SCSI Read/Write Command Timeout True
vscsi_err_recov fast_fail N/A True
vscsi_path_to 30 Virtual SCSI Path Timeout True
Confirm the new device has the updated settings for the running device.
lsattr -Pl vscsi0
rw_timeout 120 Virtual SCSI Read/Write Command Timeout True
vscsi_err_recov fast_fail N/A True
vscsi_path_to 30 Virtual SCSI Path Timeout True
There are a couple of options to implement the changes on the running devices.
Option 1 - To schedule an LPAR reboot.
Option 2 - Follow my blog post here, How to make changes to vscsi adapters without a reboot.
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