Consistency checking a block device

I’ve been testing the resizing of the drives located on a Dell MD3000, and i’ve seen errors when resizing after the 2TB mark. This is on the new firmware which supports > 2TB logical drives. I wrote a script to write to random locations of a block device. It can then read them back and verify that they’re still the same as what was written. Rather than writing to the entire device I use random sampling, with a few fixed points on the block device. I pretty much get consistent failures. If I put in the failed locations into the next write run they come out again in the subsequent run. Kind of makes resizing a dangerous operation, even though it is stated that resizing is non-destructive.

I realize that the array is nothing more than a rebrand of another device, but it would be great if it was tested in a lab before something this bad got out to the customers.


#! /usr/bin/perl -w

use strict;
use Getopt::Long;
use Digest::MD5 qw(md5_hex);
use File::Basename;

my $fs;
my $readfile;
my $writefile;

my $numpatterns = 2048;
my $seed = undef;
my $size;
my $real_size;
my $help;

my %vars;
my @def_offsets = (0);

sub usage($) {
        print <<EOM;
Usage: $0 –fs=<filesystem> –read=<file>|–write=<file>
        [--num=<number of blocks>] [--offset=<offset to test>]
        [--seed=<random number seed>]
EOM
        exit ($_[0]);
}

my $result = GetOptions( ‘fs=s‘ => \$fs,
        ‘num=i‘ => \$numpatterns,
        ‘seed=i‘ => \$seed,
        ‘read=s‘ => \$readfile,
        ‘offset=i‘ => \@def_offsets,
        ‘write=s‘ => \$writefile,
        ‘h|help‘ => \$help);

usage(0) if defined($help);
warn "Need file system to use" if (!defined($fs));
warn "Need either a read or write file" if (!(defined($readfile) || defined($writefile)));

usage (1) if (!defined($fs) || !(defined($readfile) || defined($writefile)));
my $base = basename($fs);

open (IN, "</proc/partitions") || die "Could not load partition tables";
while (<IN>) {
        chomp();
        my ($major, $minor, $blocks, $name) = m/(\w*)\s+(\w*)\s+(\w*)\s+(\w*)$/;
        next if (!defined($major));
        if ($name eq $base) {
                $real_size = $blocks;
                last;
        }
}
close(IN);

die "Could not get size" if (!defined($real_size));

# Write to the offset in blocks
sub write_to_offset($$) {
        my ($offset, $buffer) = @_;
        sysseek(INFS, $offset * 1024, 0);
        my $write = syswrite(INFS, $buffer, 1024);
        if (!defined($write) || $write != 1024) {
                warn "Failed to write: $offset $!\n";
        } else {
                $vars{$offset} = md5_hex($buffer);
        }
}

sub read_from_offset($) {
        my ($offset) = @_;
        my $buffer;
        sysseek(INFS, $offset * 1024, 0);
        my $read = sysread(INFS, $buffer, 1024);
        if (!defined($read) || $read != 1024) {
                warn "Could not read 1024 bytes at $offset $!";
                return (1);
        }
        if (md5_hex($buffer) ne $vars{$offset}) {
                warn "Data at offset $offset was not the same as expected";
                return (1);
        }
        return (0);
}

sub get_buffer {
        my $i = 0;
        my $buffer = "";
        while ($i++ < 256) {
                my $randval = int(rand(255 * 255 * 255 * 255));
                $buffer .= chr($randval >> 24) . chr(($randval >> 16) & 255) .
                        chr(($randval >> 8) & 255) . chr($randval & 255);
        }
        (length($buffer) == 1024) || die "Buffer was " . length($buffer);
        return $buffer;
}

if (defined($readfile)) {
        # reading from previous file
        open (INPUT, "<$readfile") || die "Could not open previous run log";
        while(<INPUT>) {
                chomp();
                my ($key, $value) = m/(.*)=(.*)/;
                if ($key eq "patterncount") {
                        $numpatterns = $value;
                        next;
                }
                if ($key eq "size") {
                        $size = $value;
                        next;
                }
                if ($key eq "seed") {
                        $seed = $value;
                        next;
                }
                $vars{$key} = $value;
        }
        close(INPUT);
} else {
        $seed = time ^ $$ ^ unpack "%L*", `ls -l /proc/ | gzip -f` if (!defined($seed));
        $size = $real_size if (!defined($size));
        open (OUTPUT, ">$writefile") || die "Could not open new run log";
        print OUTPUT "patterncount=$numpatterns\n" .
                "size=$size\n" .
                "seed=$seed\n";
}

print "Size: $real_size [$size] Seed: $seed\n";
srand($seed);

my $mode = "<";
$mode = "+<" if ($writefile);
open(INFS, "$mode$fs") || die "Could not open raw device";

if ($writefile) {
        map { write_to_offset($_, get_buffer()) } @def_offsets;
        write_to_offset($size - 1, get_buffer());
        while($numpatterns > 0) {
                my $offset = int(rand($size));
                print "Writing pattern: $numpatterns           \r";
                next if defined($vars{$offset});
                write_to_offset($offset, get_buffer());
                $numpatterns–;
        }
        map { print OUTPUT "$_=" . $vars{$_} . "\n" } keys(%vars);
        close(OUTPUT);
} else {
        my $failcount = 0;
        my $tocount = scalar(keys(%vars));
        map { $failcount += read_from_offset($_); printf("To Count: %0.7d\r", $tocount–); } sort(keys(%vars));
        print "Count difference: $failcount\n";
}


consistency.pl.txt