Archive for September, 2009

Ive had Replication Manager 5.2 integrated with VMware VI3, hanging off an EMC Celerra using iSCSI for some time now, and ever since vSphere was released Ive been meaning to test the functionality to make sure everything works and to see if there are any changes.

Now having set this up with 3.5 update 4 hosts I remembered one of the key steps is changing the advanced LVM.EnableResignature option to 1 which allows a snapshot of an existing lun with a matching header to  automatically re signature and be presented back to the host. If you want to read more about how this works then Chad Sakac has a really good post about this here.

 Here is a screenshot showing this on a ESX 3.5 host.

LVM

 

The next step was to build my self a vSphere 4 host and integrate it into my existing lab setup, after building the host and searching through the advanced options I realised the LVM.EnableResignature option was not available and after a quick google it didnt take long to find this post by Duncan at Yellow-Bricks.

After configuring the host in Replication Manager I performed a Mount of an existing snapshot to my vSphere1 host, the task completed successfully but I was unable to see the lun on the host.

The image below shows the snapshot has been succesfully mounted to the host.

mount

You can see only the default datastore on local disk and the original Celerra Lun is shown.

datastor

 

 

 

Next I went to Configuration >> Storage >> Add Storage >> Disk/Lun and there it was.

addstorage

 After selecting the lun and clicking next, I was now presented with three options as shown in the screenshot below.

addstorage_options

 

As Duncan pointed out in his post, yes this can be done through the GUI but its more fun from the command line, im also a firm believer of learning to do tasks from both the command line and the GUI.

So with that said im now going to use vicfg-volume to resignature the lun.

First lets check the existing header ID  using vicfg-volume.pl – -server vsphere1 -l

vicfg-volume

Now lets resignature the lun using vicfg-volume.pl – -server -r <existing_header>

resig

Next I check to see if the lun is now visible, and there it is.

snap

 

 

 

 

Just as a last note to this post I just wanted to mention Ive not yet found anything in the release notes to confirm vSphere is supported with Replication Manager 5.2.2, so at the moment this is nothing more than an informational post. Ill make sure to update this as soon as Ive confirmed this is in fact supported.

Oh and just incase you’re wondering why this change has come about…. With VI3 and LVM.EnableResignature it was an all or nothing setting, now with vSphere 4 you can change this on a per Lun basis, actually a good thing once you know about it.

If you’re a VMware shop you have to check out some of the demos online, Replication Manager is a Brilliant product !

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Something I noticed last week while working on a customers site was multiple iSCSI initiators logged into iSCSI targets which I had not granted access.

I’ll fire up my lab to demonstrate what I saw and how to change the behavior.

Here on my Celerra simulator I have three iSCSI Targets configured for VMware, Exchange and SQL. Each Target uses a different interface with its own IP address.

targets

Im going to use my Exchange Virtual Machine to demonstrate, but before I flick to the VM, I want to show the mask for the VMware and SQL iSCSI targets.

VMware –Only the vSphere initiator masked here.

vmware_target

SQL – Only the SQL initiator masked here.

sql_target

Now lets flick to the properties of the Microsoft iSCSI initiator in my Exchange VM. You can see Ive only configured the IP address assigned to the Exchange iSCSI target.

discovery

Now lets take a look to see what targets are visible.

iscsi initiator

And here you can see the iSCSI initiator is able to see all three targets. The reason for this is because by default the Celerra returns information on all targets to all initiators regardless of the lun mask.

Although the systems can only access the luns the mask permits, it’s still quite messy when you have 5, 10, 15 targets on the Celerra which are visible to all Microsoft initiators. So luckily the guys who write the code have a parameter for us to change which alters the default behavior.

First lets confirm the current setting.

[nasadmin@csprod ~]$ server_param server_2 -f iscsi -i SendTargetsMode
server_2 :
name                    = SendTargetsMode
facility_name           = iscsi
default_value           = 0
current_value           = 0
configured_value        =
user_action             = none
change_effective        = immediate
range                   = (0,1)
description             = Enables return of information about inaccessible targets

Now lets change the current value to 1

[nasadmin@csprod ~]$ server_param server_2 -facility iscsi -modify SendTargetsMode -value 1
server_2 : done

And now confirm the current vaule = 1

[nasadmin@csprod ~]$server_param server_2 -f iscsi -i SendTargetsMode
server_2 :
name                    = SendTargetsMode
facility_name           = iscsi
default_value           = 0
current_value           = 1
configured_value        = 1
user_action             = none
change_effective        = immediate
range                   = (0,1)
description             = Enables return of information about inaccessible targets

So what Ive  done here is configured the Celerra to only return information on iSCSI targets when luns have been masked to the client initiator.

Restarting the iSCSI service on the Celerra causes the initiators to drop the targets to which it has no luns maksed (Actually do this with caution as it causes all iSCSI connections to drop)

Lets take a look at  my Exchange VM after this has been done.

1target

Much Better ! If you dont use the Microsoft iSCSI initiator than this is not really going to bother you, VMware’s software initiator only shows targets when connected to luns.

In my honest opinion this should be the default setting.