LVM- Default timeout. for pvchange

[John Tyler]

What is the default timeout value before lvm changes over to alternate link if defined? I know that i need to use pvchange -t option to define the timeout for a specific disk. Is there a way to set this value for all disks.? What is the recommended timeout value?

[A. Clay Stephenson]

Hi Ven,

The default timeout value is driver specific. For the most part, the defaults work fine.
You can use pvdisplay to display the timeout values but if set to default then that is all you know. The one exception I've found that needs to be set are AutoRAID LUN's. There I would set them to 90-120 seconds. You may not be aware that once an alternate link has been used, it does not automatically switch back over once the primary is back up.

REgards, Clay

[James R. Ferguson]

Hi Ven:

It appears from Knowledge Base document #A5166495 that the default value is 30-seconds when the PV TIMEOUT value is set to zero (denoting default behavior).

...JRF...

[James R. Ferguson]

Hi again:

Also. KB item #KBRC00005073 documents the LVM 'autoswitch' parameter of 11.x.

/begin_quote/

The autoswitch parameter was added with the LVM commands patch PHCO_20870. It causes the display of the setting of the auto-switch-back parameter of the physical device, which can be set using the pvchange command.

pvchange -S y/n is used to set this option.

From the pvchange man page:

On dual controller devices, pvchange sets the permission that controls whether or not the system will automatically switch from the current controller to the original controller after the original controller has recovered from a failure. It also permits you to switch manually to a controller on the device other than the current controller.

Dual Controller devices those disk devices that have more than one physical
path to the disk device. These are usually dedicated disk racks, arrays, etc.
with multiple SCSI or Fibre Channel bus controllers in them, which provide a
secondary path for the system to access the actual disk media in the cabinet.

LVM calls these multiple physical paths to a device "alternate paths" or "pvlinks".

When these paths are configured, one of the paths is designated as the "primary" path by the order in which they are added to the Volume Group. If autoswitch is "on", and the path used to access the device switches to the
alternate because of some failure, when the primary path recovers the path used to access the device will switch back to the primary path. If autoswitch is off, the path will stay switched until the administrator intervenes.

Autoswitch = on is the default setting, and it does not do or mean anything unless you have multiple paths to the physical disk devices.

/end_quote/

...JRF...

[Kandaswamy Natarajan]

default timeout: 30 Secs

The only way is scripting.

for i in `ls /dev/dsk/*`
do
pvchange -t 120 $i
done
lvlnboot -R

[Bill McNAMARA_1]

recommended is the max time to switch from worst case failover. Typically 90 seconds for Autoraid controller failure.

Default I heard is 30 seconds, however in 11i it is 90 seconds.

You can change it with pvchange -t
Note that an alternate link will not automatically switch unless configured. pvchange -x and pvchange -s for switching policy and force switch. Once your server activates the vg it will use the first instance found in the lvmtab as the pri link.

Later,
Bill