Wrote a script at work today, one that will monitor a filesystem in AIX, and increase it's size if it begins to run out of room...Added alot of neat little trick to it, including email notification. Here's the goods:

#!/usr/bin/perl
#
# MoveCeiling v0.2 written 061206:1122 by BJP
#
# MoveCeiling will watch and automatically increase the size of an AIX filesystem
# given user-specified parameters.
#
# Usage: moveceiling       
# Example: moveceiling 500 /tmp 64 3200 5 foo@bar.com
# English: Keep 500MB free in /tmp. If you have to add space, add it in 64MB chunks. Preserve 3200MB in the volume group.
#          Remind me every 5 times you have to increase space, and send that reminder to foo@bar.com
#

use Mail::Sendmail;

$ceilingSize=$ARGV[0];
$targetFS=$ARGV[1];
$incrementSize=$ARGV[2];
$sleepTime=$ARGV[3];
$preserveAmount=$ARGV[4];
$notifyCounter=$ARGV[5];
$mailRecipient=$ARGV[6];
$mailSender=$ENV{"USER"}."\@"."localhost";

if ($#ARGV!=6)
{
        showUsage();
        exit();
}


spinUpRoutine();
mainRoutine();
spinDownRoutine();


sub showUsage()
{

        print "\n MoveCeiling's job is to watch a filesystem, and increase it's size if the\n";
        print " amount of free space in that filesystem falls below threshold. MoveCeiling\n";
        print " is much smarter than it used to be, but you should still use it with caution. \n";
        print "\n";
        print "      Usage: moveceiling       \n";
        print "    Example: moveceiling 500 /tmp 64 30 5 foo\@bar.com\n";
        print " In English: Every 30 seconds, check to see if /tmp has at least 500MB free. \n";
        print "             If it sinks below 500MB, add another 64MB. For every 5 times I \n";
        print "             add more space, i'll send a status message to foo\@bar.com.\n";
        print "\n\n";
        exit();
}


sub spinUpRoutine()
{
        print "\nMoveCeiling: I will make sure $targetFS has at least $ceilingSize MB free.";
        print "\nMoveCeiling: If I have to increase it's size, I will do so in $incrementSize MB increments.";
        print "\nMoveCeiling: Every $notifyCounter times I do so, i'll drop a note to $mailRecipient.";
        print "\nMoveCeiling: I'll stop adding storage if the volume group has less than $preserveAmount MB remaining.";
        print "\nMoveCeiling: Starting up..\n";

        ## Check to see if the filesystem actually exists...

        @dfContents=split(/\s+/,`df -m | grep " $targetFS\$"`);

        if(length($targetFS)==length($dfContents[6]))
        {
                print "MoveCeiling: Examining $dfContents[6]..\n";
        }


        else
        {
                print "MoveCeiling: Uh-oh.. Can't find the filesystem you specified ($targetFS)..!  Exiting.\n\n";
                exit();
        }

        ## So far so good. Pull up the VG info for this filesystem..

        $dfContents[0]=~/\/dev\//;
        $targetLV=$';
        @lslvContents=split(/\s+/,`lslv $targetLV|head -n1` );
        $targetVG=$lslvContents[5];

        print "MoveCeiling: $targetFS belongs to logical volume $targetLV inside $targetVG.\n";

        @lsvgDump=split(/\s+/,`lsvg -L $targetVG | head -n4 | tail -n1`);
        $lsvgDump[6]=~/\(/;
        $targetVGSpaceRemaining=$';

        print "MoveCeiling: $targetVG has $targetVGSpaceRemaining MB remaining, of which $preserveAmount MB will be preserved.\n\n";


}

sub mainRoutine()
{
        while(true)
        {
                @dfContents=split(/\s+/,`df -m | grep " $targetFS\$"`);
                chomp($dateString=`date`);

                print "MoveCeiling: $dfContents[2] MB remaining in $targetFS as of $dateString.\n";

                @lsvgDump=split(/\s+/,`lsvg -L $targetVG | head -n4 | tail -n1`);
                $lsvgDump[6]=~/\(/;
                $targetVGSpaceRemaining=$';

                if($dfContents[2] < $ceilingSize) # Tricky logic time..
                {
                        if($targetVGSpaceRemaining >= ($preserveAmount+$incrementSize))
                        {
                                print "MoveCeiling: Less than $ceilingSize MB remaining! Adding $incrementSize MB to $targetFS..\n";
                                system("echo `date` -- MoveCeiling: Less than $ceilingSize MB remaining! Adding $incrementSize MB to $targetFS.. >>/tmp/moveceiling.log");
                                `chfs -a size=+"$incrementSize"M $targetFS`;
                                $incrementCounter++;

                                if($incrementCounter==$notifyCounter)
                                {
                                        sendNotification();
                                        $incrementCounter=0;
                                }
                        }

                        else
                        {
                                system("echo `date` -- MoveCeiling: Preserve limit reached. Committing suicide. $targetFS last seen with $dfContents[2] MB free, $targetVGSpaceRemaiing MB remaining in $targetVG.  >>/tmp/moveceiling.log");

                                print "MoveCeiling: Increasing $targetFS by $incrementSize MB would eat into the preserved area! \n";
                                print "MoveCeiling: Preparing suicide note to $mailRecipient..\n";
                                sendSuicideNote();
                                print "MoveCeiling: My hands are tied! I'm sorry!\n";
                                spinDownRoutine();
                                exit();
                        }
                }

               else
                {
                        print "MoveCeiling: More than $ceilingSize MB remaining..No increase needed.\n";
                }

                print "MoveCeiling: $targetVGSpaceRemaining MB remaining in $targetVG. Sleeping for $sleepTime seconds..\n\n";
                sleep($sleepTime);
        }
}


sub sendSuicideNote()
{

        %mail=( To => $mailRecipient,
                From => $mailSender,
                Subject => "MoveCeiling Suicide Notice",
                Message => "Preserve limit reached -- Data loss may be imminent. $targetFS last seen with $dfContents[2] MB free, $targetVGSpaceRemaining MB remaining in $targetVG. );

                sendmail(%mail);

        print "MoveCeiling: Suicide note sent.\n";

}

sub sendNotification()
{
        print "MoveCeiling: Sending a friendly reminder to $mailRecipient..\n";

        %mail=( To => $mailRecipient,
                From => $mailSender,
                Subject => "MoveCeiling Update",
                Message => "$targetFS still growing. Now at $dfContents[2] MB in size with $targetVGSpaceRemaining MB remaining in $targetVG." );

                sendmail(%mail);

        print "MoveCeiling: Mail sent.\n";
}

sub spinDownRoutine()
{
        print "MoveCeiling: Spinning down..\n\n";
}