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vMWARE - presenting iSCSO to Virtual server as storage

Posted on 2011-02-23
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In VCenter (to my ESXi 4.1 host) would like to allocate a storage pool from my SAN (via iSCSI) to a virtual server (2008 R2). So basically want a Virtual Server to have an iSCSO connection to SAN. I have a dedicated NIC in my ESXi host in which I will dedicate to this, and have this directly connected to SAN appliance. I have created a vswitch and have added the correct dedicated NIC to this. I have the iSCSI settings correctly configured on SAN appliance as well. When I go to storage adapters in vcenter I do NOT see the newly created iSCSI adapter. What am I missing? All I see is an iSCSI software adapter.
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Question by:Trihimbulus
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by:kevinhsieh
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I understand that you want the guest to talk directly to your SAN via iSCSI. If that is the case VMware doesn't do anything other than to provide the networking connectivity. The other configuration is done on the SAN and guest. Basically you do it just like your guest is a physical server. The SAN needs to have the LUN configured for the guest's IP/iSCSI initiator name/CHAP credentials and the guest needs to have its iSCSI initiator configured.
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by:Trihimbulus
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OK so I do this through iSCSI inituatior on the virtual 2008 R2 server. Gotcha
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by:chkdsk01
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Yes, you can do this with the MS iSCSI initiator.  However, there are some pros and cons of the ms iscsi in guest VMs.  Check out this link.  The biggest cons of ms iscsi is no SRM and no guest quiescing during snapshots, which may or may not be important to you.  I just wanted to point them out.
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by:Trihimbulus
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chkdsk - I didn't see a link. Is there a better way to do thi, as far as presenting as storage to virt server?
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by:chkdsk01
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Sorry about the link. Hopefully this will work.
http://blog.itoncloud.com/?p=419

There is not so much a better way, but just different ways. It depends on what you currently have in your environment and what you plan on having. The fact that guest quiesing and SRM dont support ms iscsi was a deal breaker for us. Also, from my research ms iscsi provides convenience. It's easy to setup but rdm's seem to have an edge concerning performance.
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by:Trihimbulus
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"The fact that guest quiesing and SRM dont support ms iscsi was a deal breaker for us."

What does this mean and what capabilities does this take away?
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by:chkdsk01
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What I mean by "guest quiescing" is VMware snapshots.  If you've ever taken a snapshot of a virtual machine, this will not work (or is often inconsistant) on a VM with the MS iscsi initiator.  This may change, but it has been the case for a few years now.  For us, our VM backup application utilizes snapshots.  And while you can turn off the VMware quiescing, I did not like this workaround, as I would only have crash-consistant backups (crash consistant and quiesced backups is a whole other debate).  Here is a link to the kb that addresses snapshots and ms iscsi.
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1009073

Also, we are considering a purchase and implementation of SRM.  SRM is VMware's product called Site Recovery Manager.  Last I checked this product does not support VMs running the MS iscsi initiator.  

So for us, because of what we had already (backup app) and our future plans (SRM), we use RDMs any time we need direct LUN access for a VM.  And like I said before, my research points to a small performance benefit with RDMs too.  Hope this helps.
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by:juliovp01
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Hello,

Yes, the trick is using the MS iSCSI initiator, you must configure this in the Windows VM. Also you need to be sure that the SAN is handling the authentications (by IP or IQN) base on the host settings. Beyond that the VMware only works as a network switch, meaning that your NIC (the one on the iSCSI network) need to be part of the vSwitch that you have the NIC of the Virtual Machine for iSCSI as a member.
Also please check if you are using Jumbo Frames on the iSCSI network and remember enabling the capabilities on the virtual nic inside the VM in order to get a better perfomance.
Regards,
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by:Trihimbulus
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I guess another option would be to just allocate enough space on the VM to host the shares directly from the local VM Server- sloppy though....
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by:chkdsk01
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What is this server for, file server?  Can your San do CIFS?  If so, why not just pit your shares directly on your San?  Otherwise rdm is a good solution.
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by:Trihimbulus
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Nope it doesnt - what is RDM?
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by:kevinhsieh
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RDM is Raw Device Mapping. We seem to have gone from how to connect your VM to storage via iSCSI to whether or not you should. FWIW, I use the iSCSI initiator in my VMs to connect to my data volumes for my SQL, Exchange, and file servers.

http://www.virtualizationteam.com/virtualization-vmware/vmware-vi3-virtualization-vmware/dont-use-vmware-raw-device-mapping-rdm-for-performance-but.html
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by:Trihimbulus
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Since you are connecting via iSCSI Initiator in VM for file server kevinhsieh, what did you do to overcome the lack of snapshots?
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by:kevinhsieh
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I can still snap the VM, which just snaps the OS. I can just snap the data from the SAN or tell my VM to snap the SAN which integrates with VSS so that it's consistent. I am not trying to snap the whole thing from the hypervisor. I don't want to tie the OS to the data anyway. I have restored the OS to a previous version while keeping the data intact.
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by:Trihimbulus
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And you are NOT using raw device mapping right?
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by:kevinhsieh
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I am not using RDM. I am using Hyper-V. Since I am using the iSCSI initiator from inside the VM, the VM knows that it is using SAN storage and it has full access to the integration between it and storage, as opposed to trating it like a dumb SCSI disk.
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by:Trihimbulus
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OK so I am still stuck in the same dillema since I am using VMware and you are using HYper-V then?
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by:chkdsk01
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If you put your files inside the VMDK you pretty much lose the ability to do san based snapshots of the files themselves and you resort to snapping the Windows volume they are in and backing up via whatever backup software you have.  If you use RDM or the MS iSCSI initiator, you can put the files on a SAN lun and utilize san based snapshots and then perhaps a snap to tape, or whatever you choose to do.

If you want to put your files on a san lun, you really have two options, RDM or MS iSCSI inside the guest.

What type of storage do you have?
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by:Trihimbulus
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Cybernetics - you've prob never heard of it but it does do snapshots and I'm am backup up those snapshots to an external disk
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by:chkdsk01
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Ok.  Good.  So to answer your initial question, you have two options, RDM or MS iSCSI.  You need to weigh the advantages and the negatives of each and decide which way you want to design this.  

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by:Trihimbulus
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So if I do end up doing MS iSCSO- do I just add the vmnic to the same vswitch as the eSXi host or create a new vswitch? This is where I am consfused.
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chkdsk01 earned 500 total points
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You can choose to put the vNIC on a seperate vSwitch if you want (I would probably suggest this).  You could just add a new port group to an existing vSwitch but it depends on how you choose to design everything.  If you create a new vSwitch you need to assign pNICs to it.  I believe you said you have done this already.  So at this point, you can create a port group on your vSwitch, then add a vNIC to your VM and assign it to this new port group you just created.  

Now, I'm not positive about how to tell the MS iSCSI initiator to use one nic as opposed to the other, but I assume you can set permissions on the iSCSI lun on the storage to only allow the ip address of the nic that you want, and deny any other.  This is roughly how I have my ESXi environment at home, although it is with the actual hosts, not the MS initiator.  

Anyway, hope this helps.
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by:Trihimbulus
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Can you link me to an article on how to setup RDM by any chance?
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by:Trihimbulus
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Ok- when setting up Raw Device Mapping compatability mode, should I select Physical of Virtual????
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by:Trihimbulus
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and Mode - should I select Persistent or Nonpersisitent???
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by:Trihimbulus
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Looks like its time to close this as no one is replying anymore. Thanks all! I'll start a new post.
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