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Postfix, Realtime Maildir Replication Using Dual-primary DRBD with OCFS2

email, kernel, linux, load balance, modules, postfix, redhat, smtp No Responses »

Jun 192011

As I’ve been written on my previous post about Maildir Replication using ChironFS in postfix, I will explain step by step it can also be done by using drbd and ocfs2.

Compiling & Installing

note: if your Linux distribution is shipped with a kernel older than 2.6.33 you have to install a kernel module package and packages for the user land code. If your distribution contains a Linux-2.6.33 kernel or newer you only need to install the user land code.

In my case i have my linux distribution older than 2.6.33, so i will also compile drbd kernel module.

Download drbd source and create Binary RPMS packages

$ wget http://oss.linbit.com/drbd/8.3/drbd-8.3.10.tar.gz
$ tar xvzf drbd-8.3.10.tar.gz
$ cd drbd-8.3.10
$ ./configure --enable-spec --with-km
$ cp ../drbd*.tar.gz `rpm -E %_sourcedir`
$ rpmbuild -bb drbd.spec
$ rpmbuild -bb drbd-km.spec
$ sudo rpm -ivh /path/to/RPMS/drbd-*

I’ll be using loop files for this setup since I don’t have access to raw partitions. but if you have raw block device available you can subtitute this part:

resource r0 {
	meta-disk internal;
	device /dev/drbd0;
	disk /dev/loop0;

Into:

resource r0 {
	meta-disk internal;
	device /dev/drbd0;
	disk /dev/sdxx;

sdxx can be sda1, sdb1 sdb2 or what ever your raw disk device called

# dd if=/dev/zero of=/drbd-postfix.img bs=1M count=5000
# losetup /dev/loop0 /drbd-postfix.img

Place this DRBD resource file in /etc/drbd.d/r0.res. Be sure to adjust the server names and IP addresses for your servers.

resource r0 {
	meta-disk internal;
	device /dev/drbd0;
	disk /dev/loop0;

	syncer { rate 1000M; }
        net {
                allow-two-primaries;
                after-sb-0pri discard-zero-changes;
                after-sb-1pri discard-secondary;
                after-sb-2pri disconnect;
        }
	startup { become-primary-on both; }

	on postfix1 { address 192.168.200.18:7789; }
	on postfix2 { address 192.168.200.114:7789; }
}

Check Disk Quota Usage By Parsing Maildirsize

email, perl, postfix, smtp 1 Response »

May 182011

In the previous article, I have explained how to check the quota usage by using perl scripts. maildir quota checking is done by using File::Find function which seems a bit slow and too much consuming I/O process. same as the find function on bash script. find function in perl perform disk usage by determining the size of all files and directories recursively. all sizes of files and directories then accumulated.

find(sub{ -f and ( $size += -s ) }, $diruser );

actually, examination of maildir quota usage is also done by imap server which is written into a file called maildirsize. So, rather than wasting resources on the server. we can directly read the specified quota and usage on maildirsize file.

Maildir quota usage using File::Find

sub checksize {
        my $diruser = $_[0];
        trim($diruser);
        my $size;
        find(sub{ -f and ( $size += -s ) }, $diruser );
        if (defined $size) {
                $size = sprintf("%u",$size);
                return $size;
        }
        return undef;
}

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