Folder deletion did not remove files from disc

[Tim Bannister]

Recently we saw what we hope is a one-off error on our Cyrus deployment
here. This is Cyrus 2.3.7 on x86_64 RHEL4 based on Simon Matter's RPMs.
I'd used IMAP as "cyrus" to delete a number of users. This is done using
some rather old code:
    # Change ACL for mailbox to be deleted

    $err = $imap->set_acl("user.$username", "cyrus", "lrswipdca");
    if ($err != 0) {
        print "$imap->{'Error'}\n";
    }

    # Delete mailbox

    $err = $imap->delete("user.$username");
    if ($err != 0) {
        print "$imap->{'Error'}\n";
    }

All these mailboxes disappeared from the output of "ctl_mboxlist -d" as
I'd expect, but some remained on the filesystem. I didn't see a pattern
to which these were.

I'd like to know if anyone has seen this before and any suggestions for
a cause / remedy. I have NOT been able to replicate the problem myself
but it is nevertheless a cause for some concern.

-- 
Tim Bannister
IT Services

e: Tim.Bannister at manchester.ac.uk
w: http://www.manchester.ac.uk/itservices