VDO Troubles

Once in a while, on very large VDO volumes, storage just dissapears.  In my case I had one 42TB volume that just refused to boot.  Here are some of the symptoms:

• Boot dropped single user into a shell
• "vdo start" says the vdo volume was already started, but there is no entry in /dev/mapper/.

In this case I retried "vdo stop" then "vdo start" a few times until the vdo volume became available.

Further observation implies that systemd kills the vdo startup process.  What happened was that vdo was interrupted on its long boot up---a timing issue.

A working solution for me was to include a timeout value in /etc/fstab for the particular vdo volumes:

# /etc/fstab
 /dev/vgsample/lvsample /somedirectory ext4 defaults,discard,x-systemd.requires=vdo.service,x-systemd.device-timeout=10min 0 0

Working so far, survived a few reboots.

JondZ 20181031