[stgt] SCSI ID uniqueness: VMware initiator

[Yaron Sheffer]

Hi Fujita,

thanks for your response, much appreciated. Please see below.

     Yaron

On 10/25/2012 07:46 AM, FUJITA Tomonori wrote:
> [...]
>> * target name needs to be globally unique.
>>
>> Trying to work around the issue, we attempted to set the SCSI ID
>> parameter for the LUN using this command: tgtadm --mode logicalunit
>> --op update --tid $tid --lun $lun --params scsi_id="my id"
>>
>>
>> * This syntax is undocumented. Can you please add it to the man page? Or
>> * can I provide such a patch?
> Please send the patch. I'll merge it.

Attached.
> [...]
>> Finally we just randomized the target ID value, which causes tgtadm to
>> generate a somewhat randomized SCSI ID, and makes VMware happy. We
>> also patched tgt-admin to dump the tid value and accept it back in its
>> "execute" mode. I will gladly share this patch, but I suspect that it
>> is the wrong thing to do from an architectural POV. Any opinions?
> scsi id is supposed to be parsistent after reboot. We can't use random
> values every time.
Sure, we persist the configuration (*including* the tid value) with the 
patched tgt-admin. The SCSI_ID is derived from the tid, so it does not 
change after reboot. It would have been better to persist SCSI_ID 
directly, but then we would have to change the format of the tgt-admin 
config file rather drastically. The format is extensible enough to 
support per-target parameters, but not per-LUN parameters.

I am attaching the tgt-admin patch, although I don't think it is the 
"right" way of solving this problem.

-- 

*Yaron Sheffer*|Co-Founder and CTO, *Porticor Cloud Security*| T:+972 73 
7294673 <tel:+972-73-7294673> | M:+972 52 8698984 <tel:+972-52-8698984> 
| yaronf at porticor.com <mailto:yaronf at porticor.com> |www.porticor.com 
<http://www.porticor.com/>

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--- /usr/sbin/tgt-admin.orig	2012-10-15 08:28:00.932922867 -0700
+++ tgt-admin	2012-10-16 07:02:17.448209072 -0700
@@ -35,6 +35,7 @@
   -p, --pretend			only print tgtadm options
       --dump			dump current tgtd configuration (note: does not
 				include detailed parameters, like write caching)
+      --fix-tid			dump (and respectfully, restore) the target's TID
   -v, --verbose			increase verbosity (show tgtadm commands)
   -h, --help			show this help
 
@@ -53,6 +54,7 @@
 my $alternate_conf="0";
 my $ignore_errors = 0;
 my $force = 0;
+my $fix_tid = 0;
 my $pretend = 0;
 my $dump = 0;
 my $verbose = 0;
@@ -66,6 +68,7 @@
 	"s|show"        => \$show,
 	"c|conf=s"      => \$alternate_conf,
 	"ignore-errors" => \$ignore_errors,
+	"fix-tid"	=> \$fix_tid,
 	"f|force"       => \$force,
 	"p|pretend"     => \$pretend,
 	"dump"          => \$dump,
@@ -200,8 +203,10 @@
 					{
 					# We have to find available tid
 					if ($in_configfile == 1 && $configured == 0 && $pretend == 0) {
-						my $maxtid = find_max_tid();
-						$next_tid = $maxtid + 1;
+						if ($fix_tid == 0) {
+							my $maxtid = find_max_tid();
+							$next_tid = $maxtid + 1;
+						}
 					} elsif (length $single_target && $configured == 1) {
 						$next_tid = $tgtadm_output_tid{$target};
 					} else {
@@ -226,12 +231,22 @@
 					if (not defined $target_options{"driver"}) {
 						$target_options{"driver"} = $default_driver;
 					}
+					if ($fix_tid == 1) {
+						if (not defined $target_options{"tid"}) {
+							print "Running in fix-tid mode, but tid not defined";
+							exit 1;
+						}
+						$next_tid = $target_options{"tid"};
+					}
 					my $driver = $target_options{"driver"};
 					execute("# Adding target: $target");
 					execute("tgtadm --lld $driver --op new --mode target --tid $next_tid -T $target");
 					foreach my $k3 (sort keys %{$conf{$k}{$k2}}) {
 						$option = $k3;
 						$value = $conf{$k}{$k2}{$k3};
+						if ($option eq "tid") {
+							next;
+						}
 						check_value($value);
 						process_options($target_options_ref,$data_key);
 						# If there was no option called "initiator-address", it means
@@ -752,6 +767,10 @@
 		my $target_name = show_target_info($current_target, "target_name");
 		print "<target $target_name>\n";
 
+		if ($fix_tid == 1) {
+			print "\ttid " . $tgtadm_output_tid{$target_name} . "\n";
+		}
+
 		if (scalar @drivers_combined_uniq gt 1) {
 			my $driver = show_target_info($current_target, "driver");
 			print "\tdriver $driver\n";
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