Hi there,

After being extremely impressed from implementing it in some customer installations, I've decided to migrate our mail infrastructure to dovecot. Being able to have /bin/checkpassword support across the board for pop, imap, and smtp authentication, as well as being able to ditch stunnel for the SSL layer...where were you in 2001?!? :)

I have two concerns, the first is about the proper index configuration in our environment, and the second is about the best way to migrate mailboxes.

Some quick background: we've long been distributed, with an L4 switch up front and a Netapp in the back, Mysql for metadata. We have a cluster of several FreeBSD boxes doing filtering and maildir delivery (postfix/amavisd-new), and we have a server that users get sent to for pop/imap. If it's down, they get sent to one of the filter boxes instead.

So, regarding the indexes:

From reading the docs, it appears I would not be able to use the dovecot LDA due to locking issues (bummer), and I should configure dovecot to store index files on a local disk of the primary pop/imap server rather than on the netapp.

My first question would be, how much of a performance hit should I expect from having to update the indexes when mail is checked rather then when mail is delivered since I can't use the LDA? Is this a minor issue like I expect, or can it be something the user actually notices when checking mail?

In a worst case scenario, if the pop/imap server is down, and another server is used, how long would it take to create an index for an account with a few hundered megs, several thousand messages? I'm wondering if, since I have plenty of overhead available on the netapp, I should just store the indexes there in case another server must be used.

I'm basically looking for more information about the pros and cons of storing the indexes on the nfs volume in a situation where a single server would normally be providing pop/imap service.

Regarding migration:

My concerns regarding migration relate to how best to process existing maildirs by both converting the previous imap metadata and calculating an initial index for each account.

First off, I can't seem to find any info on a way to create an initial index file for all of the mailboxes. Can anybody suggest a command I can use for this? I'm sure I just overlooked it.

Regarding the migrations, we have both courier and bincimap to deal with. (We use qmail's pop, so no complications with migrating courier).

Fortunately, courier is used for normal imap on 143, bincimap is only used for webmail. So, it would seem that metadata from bincimap could be ignored; the only thing it would seem important to preserve is mailbox subscriptions. Please correct this assumption if I'm wrong.

bincimap uses a INBOX/folder format in the subscription file, however the actual folders are stored exactly the same as the INBOX.folder style of courier.

So, it seems like my best option is to modify the courier-dovecot-migrate.pl script to consider the mailboxes subscribed to via bincimap. Here's a modified convert_subscriptions that seems to work well in limited testing, feel free to point out any idiot mistakes, it's been a while since I've done anything substantial in perl. I would have sent a patch but I suspect I'm the only person who will ever use this change and critiquing it would be easier with a full context.

sub convert_subscriptions { my ($dir, $owner_uid, $owner_gid) = @_; my $in_fname = "$dir/courierimapsubscribed";

# ADDED: The bincimap file to parse

my $in_fname2 = "$dir/.bincimap-subscribed"; my $out_fname = "$dir/subscriptions";

# MODIFIED: Return only if neither exist

return if (!-f $in_fname && !-f $in_fname2); if (!$overwrite && -f $out_fname) { print "$out_fname already exists, not overwritten\n" if (!$quiet); return; } return if (!$do_conversion);

my ($fin, $fin2, $fout); open ($fin, $in_fname) || die $!; open ($fin2, $in_fname2) || die $!; open ($fout, ">$out_fname") || die $!;

# ADDED: An array to track mailboxes we've written in case both files exist

my @subs; while (<$fin>) { chomp $_; if (/^INBOX$/i) { print $fout "INBOX\n"; push @subs, "INBOX\n"; } elsif (/^INBOX\.(.*)$/i) { print $fout "$1\n"; push @subs, "$1\n"; } else { # unknown. keep it as-is. print $fout "$_\n"; push @subs, "$_\n";
} } close $fin;

# ADDED: A second loop, same as the first, but also checking to make # sure that the mailbox has not already been written to the new file to # eliminate duplicates.

while (<$fin2>) { chomp $_; my $sub = $_; if (/^INBOX$/i && !grep (/^INBOX\n/i, @subs)) { print $fout "INBOX\n"; } elsif (/^INBOX\/(.*)$/i && !grep (/^$1\n/i, @subs)) { print $fout "$1\n"; } elsif (!grep(/^$sub\n/, @subs)) { # unknown. keep it as-is. print $fout "$sub\n";
} } close $fin; close $fin2; close $fout; chown $owner_uid, $owner_gid, $out_fname; }

Thanks in advance for any help or suggestions! Andy

Andy Dills Xecunet, Inc. www.xecu.net 301-682-9972