RE: qpopper file locks - toasters

7 Aug 2001


      You don't mention whether or not you'll have more than
one HP-UX system accessing the mail spool.  If it's just one,
then no problem, stop reading here.  If more than one system 
can access the same mailbox (i.e. load balancing), read on.
There are two mailbox formats commonly used.  One is 
'mbox' the other is 'maildir'.  'mbox' format mailboxes
are the most common.  They use one file for multiple messages.
File locking is always an issue with this format.  
'maildir' format is one file per message.  This format
is generally headache-free in terms of file locking.
My experience is that relying on lockd for file locking
works 99.9...% of the time.  Your milage can and will
vary here.
Not all NFS clients are made the same.  Some UNIX vendors
have better NFS and NLM (Network Lock Manager) clients than 
others.  While I don't have direct experience with HP-UX,
in small environments, lockd should work fine.  (Although 
in a past life, I've run a F630 cluster with at least 8 Solaris 
based clients and 250,000 mailboxes relying on lockd with no problems.)
If you run into problems, then you should convert to the 
maildir format.  This will require that you patch or change your 
local delivery agent (the program that sendmail calls to actually
write the email to a file, probably mail.local) and your
qpopper.
Aaron
...
-----Original Message-----
From: Todd Watson [mailto:tkw@southwestern.edu]
Sent: Tuesday, August 07, 2001 3:34 PM
To: toasters@mathworks.com
Subject: qpopper file locks
My apologies if this question has been hashed over before on the list,
but the archives seem inaccessible at the moment.
We are planning on migrating our mail spool files from an HP-UX server
to our 740 filer and then mounting them back via NFS.  This HP system
runs sendmail and pop (qpopper specifically).  We are concerned about
file-locking issues which may arise or any other "gotchas" that we
should be aware of.
Thanks!
Todd
    Todd K. Watson
    Senior System & Network Administrator
    Southwestern University, Georgetown, TX
    tkw@southwestern.edu || TEL:512.863.1508 || FAX:512.863.1605