#!/usr/bin/env perl
#
# Description: Basic check if I/O scheduler and discard option on Linux servers
#              Results are displayed on stdout or redirected to a file
#
# Last Update:  24 July 2014
# Designed by:  Dusan U. Baljevic (dusan.baljevic@ieee.org)
# Coded by:     Dusan U. Baljevic (dusan.baljevic@ieee.org)
# 
# Copyright 2006-2015 Dusan Baljevic
# 
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
# The script has been developed over several hectic days, so errors
# (although not planned) might exist. Please use with care.
# 
# There are not many comments throught the script and that
# is not best practices for writing good code. However,
# I view this script as a learning tool for system administrators
# too so lack of comments is partially left as an exercise.
#

$ENV{'PATH'} = "/bin:/usr/sbin:/sbin:/usr/bin:/usr/local/bin";

use strict;

my @lsblk = `lsblk -f 2>/dev/null`;
if ( "@lsblk" ) {
    print "INFO: File systems and raids\n";
    print @lsblk;
}

my @lsblkdet = `lsblk -t 2>/dev/null`;
if ( "@lsblkdet" ) {
    print "\nINFO: Block devices\n";
    print @lsblkdet;
}

my $DISKTYPE = q{};
my $DISCARD  = q{};

if ( open( LSBK, "lsblk -io KNAME,TYPE,SCHED,ROTA,DISC-GRAN,DISC-MAX |" ) ) {
    print "\nINFO: I/O elevator (scheduler) and discard support summary\n";
    while (<LSBK>) {
       next if ( grep( /^$/, $_ ) );
       chomp($_);
       my @LSLN = split( /\s+/, $_ );

       # For virtual disks, elevator settings apply only on older kernels
       # (before 3.13). This behavior was changed in the kernel because
       # it does not make sense to run an elevator on virtual devices.
       # The same applies on bare metal for LVM and RAID: they no longer
       # have their own elevator. Instead the IO is passed straightxi
       # down the stack to the real disk where there is a single elevator
       # managing all IO to that disk, whether it comes from different
       # virtual machines, or logical volumes...
       #
       # For "real" disk devices, an example:
       #
       # cat /sys/block/sda/queue/scheduler 
       # noop anticipatory [deadline] cfq  
       #
       my $DTYPE = $LSLN[1];
       if ( "$DTYPE" eq "disk" ) {
           my $DISCMAX = $LSLN[$#LSLN];
           my $DISCGRAN = $LSLN[$#LSLN - 1];
           my $ROTATION = $LSLN[$#LSLN - 2];
           my $DNAME = $LSLN[0];
           my $DNAMECNF = "/sys/block/${DNAME}/queue/scheduler";
           my $SCHED = $LSLN[$#LSLN - 3];
           my $SCHED2 = q{};
           if ( "$ROTATION" == 0 ) {
               $DISKTYPE = "SSD";
           }
           else {
               $DISKTYPE = "Hard Disk";
           }

           if ( ("$DISCMAX" > 0) && ("$DISCGRAN" > 0) ) {
               $DISCARD = "supports discard operation";
           }
           else {
               $DISCARD = q{};
           }

           if ( "$SCHED" eq "disk" ) {
               $SCHED = "UNDEFINED";
               $SCHED2 = `cat $DNAMECNF 2>/dev/null`;
               chomp($SCHED2);
           }

           print "INFO: $DISKTYPE $DNAME configured with I/O scheduler \"$SCHED\" $DISCARD\n";
           if ( "$SCHED2" ) {
               print "INFO: $DNAMECNF contents: \"$SCHED2\"\n";
           }
        }
    }
    close(LSBK);
}

exit(0);