Red Hat Bugzilla – Bug 1301073
DM_MULTIPATH_TIMESTAMP among udev properties when device is no longer multipathed
Last modified: 2016-02-11 23:16:02 EST
Description of problem:
This value hangs around in a device's udev properties even when device is no longer multipathed. Other DM_MULTIPATH_* values disappear.
Version-Release number of selected component (if applicable):
Name : device-mapper-multipath
Arch : x86_64
Version : 0.4.9
Release : 85.el7
Size : 178 k
Repo : installed
From repo : RHEL-7
Steps to Reproduce:
1. Remove some multipath devices from a group.
2. Use udevadm to list their udev properties.
3. Notice that DM_MULTIPATH_TIMESTAMP remains even while other DM_MULTIPATH_* properties are gone.
DM_MULTIPATH_TIMESTAMP remains, other DM_MULTIPATH_* properties gone.
I was a little surprised to see any DM_MULTIPATH_* properties remaining for the device.
This may be quite deliberate, but even a reboot doesn't seem to clear it.
DM_MULTIPATH_TIMESTAMP will always be there when multipathing is enabled and multipathd is running. It's purpose it to cut down on how often multipath has to check if a device is a multipath path. This can take a bit of time, so we don't want to check on every change event. Instead, multipathd updates a timestamp whenever a new path device is discovered for the first time, or the configuration file is reloaded. When a change event happens, the device checks its existing timestamp value against the current one, and if it has changed, multipath will recheck the path.