How can disk label get lost?

[Yong Huang]

> Have you checked active paths when the label is empty?  What does
> 'service oracleasm listdisks' show when the label is missing?

About a week ago, we ran that and indeed two of the four disks were missing. With Oracle support online, we ran '/etc/init.d/oracleasm force-renamedisk' to add the labels back. And 'oracleasm listdisks' showed all four disks. But I forgot to check with 'blkid'.

Two days ago, I ran 'blkid' as oracle and saw missing labels. Yesterday, 'blkid' showed the labels correctly. Then I realized running 'blkid' as non-root simply reads the cache file /etc/blkid/blkid.tab, and running it as root updates it (and sometimes the file has to be rm'ed to be updated, or rather, created correctly). So it's possible somebody as root ran 'blkid' between two days ago and yesterday, and the cache file had a timestamp after 4pm of two days ago. But nobody here said they ran 'blkid' at that time.

Regardless the fact that root 'blkid' updates the cache file, how was the label missing at some point in time in the first place? We just opened a ticket with Red Hat, who directed us to
http://kbase.redhat.com/faq/docs/DOC-21833
It appears to be relevant, but it's really not. It doesn't answer the question how the cache file initially got incorrect info, unless of course somebody manually edited it.

Yong Huang