Condition of ODA on certain RDM LUN

Similar Questions

• List RDM LUN ID for a virtual machine

  Hi all

  I'm not able to get the LUN ID of the ROW of the virtual machine through Powercli

  Since the script below, I am able to get the following details, but not the ID. The RDM LUN are implored them to EMC VNX and assigned to virtual machines.

  Get - VM vm1. Get-hard drive - DiskType "RawPhysical", "RawVirtual" | Select name, DiskType, ScsiCanonicalName, DeviceName, Parent, CapacityGB | FL

  Output:

  Parent	: vm1
  Name	: Hard drive 3
  DiskType	: RawPhysical

  ScsiCanonicalName: naa.6000144000000010706334e594fc67d8

  DeviceName	: vml.02001700006000144000000010706334e594fc67d8496e76697378
  CapacityGB	: 200

  GUI, I see the ID LUN 23, change the VM setting > select RDM > manage paths > where I can see the LUN ID of the RDM. I would like to retrieve the ID of the LUN of Powercli.

  Help, please.

  -Malfoy

  There you go

  @"
  ===============================================================================
  Title: rdm.ps1
  Description: get all VMs with RDM.
  Usage: .\rdm.ps1
  Date: 10/20/2104
  Author: Sascha Tetzel
  Output:
  VMName        : ntsv2.xxx.local
  VMHost        : psvi08.xxx.local
  HDDeviceName  : vml.02001c00006001438005de7f650000700002ed0000485356343530
  HDName        : Harddisk 7
  HDFileName    : [prod02] ntsv2.xxx.local/ntsv2_6.vmdk
  HDMode        : physicalMode
  HDsize        : 1024
  HDDisplayName : naa.6001438005de7f650000700002ed0000
  LUN           : 28
  
  VMName        : pvsdb03.xxx.local
  VMHost        : psvi10.xxx.local
  HDDeviceName  : vml.02001d0000600508b40010735100011000023e0000485356343530
  HDName        : Harddisk 2
  HDFileName    : [prod02] pvsdb03.xxx.local/pvsdb03_1.vmdk
  HDMode        : virtualMode
  HDsize        : 260
  HDDisplayName : naa.600508b40010735100011000023e0000
  LUN           : 29
  ===============================================================================
  "@
  add-pssnapin VMware.VimAutomation.Core
  Connect-VIServer -Server vcenter
  $report = @()
  $vms = Get-VM | Get-View
  foreach($vm in $vms) {
      foreach($dev in $vm.Config.Hardware.Device){
          if(($dev.gettype()).Name -eq "VirtualDisk"){
              if(($dev.Backing.CompatibilityMode -eq "physicalMode") -or ($dev.Backing.CompatibilityMode -eq "virtualMode")){
                  $row = "" | select VMName, VMHost, HDDeviceName, HDName, HDFileName, HDMode, HDsize, HDDisplayName, LUN
                  $row.VMName = $vm.Name
                  $esx = Get-View $vm.Runtime.Host
                  $row.VMHost = ($esx).Name
                  $row.HDDeviceName = $dev.Backing.DeviceName
                  $row.HDName = $dev.DeviceInfo.Label
                  $row.HDFileName = $dev.Backing.FileName
                  $row.HDMode = $dev.Backing.CompatibilityMode
                  $row.HDSize = [system.math]::Round($dev.CapacityInKB / 1048576)
                  $row.HDDisplayName = ($esx.Config.StorageDevice.ScsiLun | where {$_.Uuid -eq $dev.Backing.LunUuid}).CanonicalName
                  $lun = Get-ScsiLun -VmHost $row.VMHost -CanonicalName $row.HDDisplayName
                  $row.LUN = $lun.RuntimeName.SubString($lun.RuntimeName.LastIndexof("L")+1)
                  $report += $row
              }
           }
      }
  }
  $report
  

• Political multi-channel Fixed and enter preffered paths balance for a set of RDM Lun

  Hi all

  I was hoping that someone with some experience PowerCLI might help me with the following problem.

  Short version:

  I need to adapt this script http://vmjunkie.wordpress.com/2009/01/29/balancing-lun-paths-on-your-esx-hosts-with-powershell/ to accept the entry of a canonical name text file...

  Long version:

  We have a number of LUNS of RDM used by Microsoft the Failover Clusters, in accordance with the recommendation from the storage provider (Dell), we need to define all teas LUN to have a multi-path of FIXED policy and want to balance these on both paths.

  I can get the canonical name for each LUN RDM using this script;

  Get-VM-Location"Cluster Name" | Get-HardDisk -DiskType "RawPhysical","RawVirtual"| SelectParent,Name,DiskType,ScsiCanonicalName

  (Of http://www.definit.co.uk/2013/03/powercli-script-to-set-rdm-luns-to-perennially-reserved-fixes-slow-boot-of-esxi-5-1-with-mscs-rdms/#more-1526( )

  I then manually identify the LUNS that have to be changed since the text output.  So, basically, I have a text file containing the canonical each of the RDM LUN name I need to change to fixed.

  LUNS.txt

  NAA.6000d31000331e0000000000000000c0

  NAA.6000d31000331e0000000000000000c1

  NAA.6000d31000331e0000000000000000c2

  NAA.6000d31000331e0000000000000000c3

  NAA.6000d31000331e0000000000000000c4

  NAA.6000d31000331e0000000000000000c5

  I can't run this command to set the Fixed multichannel strategy because I need the PreferredPath variable.

  Get-vmhost 'host name ' | Get-scsilun 'naa.6000d31000331e0000000000000000c0 ' | game-scsilun - multipathpolicy 'Fixed '.

  
  

  "If the MultipathPolicy parameter is set to 'Fixed', you must specify the parameter of PreferredPath."

  I can then get the paths by using this command:

  Get-vmhost 'host name ' | Get-scsilun 'naa.6000d31000331e0000000000000000c0 ' | Get-scsilunpath

  Favorite SanID state name
  ----       -----                                    -----      ---------
  FC.2000... False Active 50:00:D3:10:00:33:1e:19
  FC.2000... False Active 50:00:D3:10:00:33:1e:1 has

  Basically, I need to adapt this script (from here http://vmjunkie.wordpress.com/2009/01/29/balancing-lun-paths-on-your-esx-hosts-with-powershell/) at the entrance to a text file of canonical names.

  # Cluster-wide LUN Path Load Balancing Script

  # Written by Justin Emerson, http://vmjunkie.wordpress.com

  # Idea originally from a PERL script I saw here:

  #    http://www.yellow-bricks.com/2008/04/01/load-balancing-activeactive-sans/

  # This script requires the VI Toolkit version 1.5

  # NOTE: This script assumes that every LUN has the same number of paths.

  #       If you have multiple storage arrays, and they have different numbers of paths,

  #       I make no guarentees that this will work!

  # If you have an improvement to this script, please feel free to leave a comment on my blog!

  Write-Host"This script will modify the policy of all your shared LUNs on all ESX Servers"-ForegroundColorCyan

  Write-Host"in a Cluster to Fixed and select a preferred path in a round-robin fashion."-ForegroundColorCyan

  if ($args.Length -eq0) {$clusterName= Read-Host"Please enter the Cluster name"} else {$clusterName= $args[0]}

  $VMHosts= Get-Cluster$clusterName| Get-VMHost

  # Run through this loop for each host in the cluster

  foreach($VMHostin $VMHosts)

  {

      # Keep only disks of luntype "disk" to avoid any storageArrayController devices.

      # Filter to only objects where the ConsoleDeviceName starts with vml to avoid any DAS disks.

      # Note: I have tested both HP EVA and Xiotech storage and SAN LUNs always appear this way.

      # Please check if this is the same on your storage before running.

      $luns= $VMHost|get-scsilun-luntypedisk|

      where-object{$_.ConsoleDeviceName -like"/vmfs/devices/disks/vml*"}|Sort-ObjectCanonicalName

      $firstLUNPaths= Get-ScsiLunPath$luns[0]

      $numPaths= $firstLUNPaths.Length

      $count= 0

      foreach($lunin $luns)

      {

          if ($count-ge$numPaths) { $count= 0 }

          $paths= Get-ScsiLunPath-ScsiLun$lun

          $lun|Set-ScsiLun-MultipathPolicyFixed -PreferredPath$paths[$count]

          $count+= 1

          # Sleep for 30 seconds as I've heard some arrays dont like doing this too fast.

          Start-Sleep-Seconds30

      }

  }

  Any help would be greatly appreciated.

  See you soon,.

  Patrick

  Do you have something like this in mind?

  $esxName = "MyEsx" $lunFile = "./luns.txt"
  $lunNames = Get-Content $lunFile $VMHost = Get-VMHost -Name $esxName
  # Find the LUN with the least number of paths
  $leastLUNPaths = Get-ScsiLun -VmHost $VMHost -LunType disk | Sort-Object -Descending -Property {
    Get-ScsiLunPath -ScsiLun $_ | Measure-Object | Select -ExpandProperty Count} | Select -First 1 | Get-ScsiLunPath
  $numPaths = $leastLUNPaths.Length
  $count = 0 foreach ($lunName in $lunNames)
  {
    $lun = Get-ScsiLun $lunName -VmHost $VMHost  if ($count -ge $numPaths) { $count = 0 }
    $paths = Get-ScsiLunPath -ScsiLun $lun  $lun|Set-ScsiLun -MultipathPolicy Fixed -PreferredPath $paths[$count]
    $count += 1  # Sleep for 30 seconds as I've heard some arrays dont like doing this too fast.
    Start-Sleep -Seconds 30}
  

• removal of the RDM LUN

  I am aware that when you remove data warehouses, you should hide, as in article

  http://KB.VMware.com/selfservice/microsites/search.do?language=en_US & cmd = displayKC & externalId = 1015084

  Is this also the case with RDM lun. I think you need remove the discs RDM virtual machine first, but do you need to hide them before the LUN is registered to the host?

  Yes, the procedure would be the same.

• Add new storage "opération TimedOut" with RDM LUN on host. Pls Help

  Hello

  Installation program:

  4 ESX 3.5 hosts each with 2 HBA adapter connected to the HP MSA1000.

  Question:

  I set up MSCS SQL 2000 with RDM through host, MSCS failover without problem, performance wise is not a problem at all too. But the problem is that if the MSCS SQL resource is managed by the Active virtual machine that is running on host1, I can navigate to storage / adding LUNs, set in shape of new LUN with no problems.

  If I want to add new storage on the other host "host2" I received the error "Tor time to ask"is it because of the resource ROW being busy serving the machine virtual active it is why the host not allowing do not change with the addition of new storage?

  Guests see these LUNs. I can add the data store or to do a new analysis also long the LUNS are not presented to the host. Also I can browse the data store, able to see the addition of Storge Wizard when adding new

  Data store and make a new analysis only on the host where the operation of the active node. Suppose the preseneted RDM LUN on host1 and host2 and VM SQL running on host1, I can only browse the data warehouses, a new analysis and add new storge to this host. I can't do the same thing with

  hosts2.

  But if I take these "RDM LUN" LUNS in host2, host3 and host4. I can do a rescan, adding other LUNS as the RDM presented to the virtual machine, able to see the add storage wizard.

  I googled the error and found that the Ontario server is question, or DNS

  Best regards

  Hussain Al Sayed

  Post edited by: habibalby

  I had similar questions to those two problems here where I couldn't add a data store as he would expire and I got the long startup time. I also use RDM which I use for MSCS in the whole of boxes 2. Here's a quote from my previous post in which I found a response that helped me. Changingthe SCSI retry time increased my boot time and allowed me to add one more time without the question of the time-out, data warehouses.

  Response to previous Post:

  I did some research and I think I've made some progress. I found that I get lots of SCSI errors in the VMkernel newspaper. I did some more research and found out that I can change the time retrying SCSI 80 to 10 and it has done wonders for my time to reboot. Now, instead of taking 20 minutes to start, it takes less than 5 minutes now. Much better. I made the change in the host-> advance-> SCSI--> SCSI configuration try again. 80 a the default and 10A was suggested as being a good value. It helped and I will keep an eye on what can make the effect, but so far it has helped with startup times.

  http://communities.VMware.com//thread/203122?TSTART=0

• Please specify disadvantage of RDM, and how to modify vmfs to RDM lun?

  I read through many threads and still do not understand the disadvantage of RDM.

  #1 so, technically, the virtual machine is that a pointer to the SAN with RDM lun, correct? I could introduce this RDM drive easily to any server and see the data, and there may be a slight performance with RDM advantage.

  If this is the case, what is the advantage of VMFS to RDM with a SAN?

  #2 can a san LUN be divided into RDM disks will different VM?

  #3 if I have a unused 600GO VMFS san lun and want to make that a lun RDM, how should I do this? I need to fdisk and unformat the thing first? Then remove from storage and add?

  With the help of ESX 3.5 Update 2 and vCenter 2.5 Update 2.

  Thank you.

  #1 so, technically, the virtual machine is that a pointer to the SAN with RDM lun, correct? I could introduce this RDM drive easily to any server and see the data, and there may be a slight performance with RDM advantage.

  Fix.

  If this is the case, what is the advantage of VMFS to RDM with a SAN?

  VMFS advantages are that you can put a lot of virtual disks on a single volume.  Its a one-to-many relationship when the RDM is a one-to-one relationship to a logic unit number by computer virtual.  There is currently a maximum of 256 LUNS per ESX host, so if you had a large number of virtual machines you could get into trouble in this way.  3 RDM by 100 hosts would be a problem.  Another consideration is that the RDM add more it, the more you complicate the management of your storage environment.  Its much easier to manage a LUN 3 or 4 to 30-40 of them.  Usually the RDM are perfect when you need of MSCS, want to take advantage of the options of SAN backup, or if you have LUNS that must be transferred to a physical server at a given time.

  #2 can a san LUN be divided into RDM disks will different VM?

  I think that you do not want to break the LUNS as well.  Its much easier to manage these relationships 1-1.

  #3 if I have a unused 600GO VMFS san lun and want to make that a lun RDM, how should I do this? I need to fdisk and unformat the thing first? Then remove from storage and add?

  Not exactly, but I think you could remove the ESX host data store and then add it as an RDM to a virtual machine.  Fdisk should be able to fix it!  But back to the point 2 - it might make more logical management of skin only 600 GB and distribute according to needs.

  Good luck!

• RDM and extend a RDM LUN

  Little again in RDM use. Object have sharing files from 500 GB and virtual machine that will grow largs. Is not supposed to have a physical file that big top on VMFS.

  Open a ticket with VMware support. My question is when comes the time to extend the LUN the WDR points to what is the process?

  I thought that the Group SAN would use there tools to extend the LUN (vm is still upward and the operation (Server 2003)), I would do a new analysis inside the BONE and because I used a dynamic disk, extend the volume with Disk Manager.

  VMware support says it's process: team SAN extends the LUN (possibly vm down during this time), Rescan HBAS on the ESX servers to see the new size, we must bring down the virtual machine, remove the RDM disk and add it to update the new size, and then inside the BONE expand the volume with Disk Manager.

  I would really appreciate someone with lots of experience RDM give some feedback.

  Oh, I used virtual compatibility mode on the ROW, but can get in physical mode if it is better.

  POINTS WILL BE AWARDED!

  Check this thread for your answer.

  http://communities.VMware.com/thread/81543

  and you want mode physics Computability (can always quarterback to virtual when finished).

• MSCS with a RDM SAN LUN

  I'm building a Microsoft Cluster with two VM on the physical host computers separate servers.  Based on what I have read so far using a RDM SAN LUN is supported when the cluster nodes are on separate host servers.  VMFS formatted SAN LUNS are not supported when the nodes are on separate host servers.

  If I have I need of several shared volumes, the only commune RDM LUN can cause several volumes in windows or each shared volume is associated with a RDM LUN?

  ESXi 5.0

  Windows Server Standard 2008 R2 x 64-cluster nodes

  Welcome to the community,

  usually, you would create a volume on a LUN (essentially identical with the physical installation of MSCS). Having multiple volumes on a single LUN would make not much sense anyway, because MSCS can not move LUN between nodes (i.e. only a single cluster node can be the owner/Defender).

  André

• Problem ID LUN RDM clustered

  Hello!

  First of all, I have to describe how it looks my Vmware vSphere environment. In a cluster HA/DRS, I have five ESX 4.0 ESX and U2 all are connected to EMC san. I have a virtual machine that introduced the RDM lun. RDM lun is virtual mode. The problem is that I added an ESX later than the others and now this ESX has different LUN id and I can not migrate this virtual machine to the ESX. I know that all RDM LUN must be the same, but how do I fix this.

  Any idea to solve this problem?

  Concerning

  hhmz

  You must keep the same unit number lun logic on all hosts.

  masking the LUNs on EMC san for the other hosts to redo

  Binoche, VMware VCP, Cisco CCNA

• Size of the LUN. Urgent request.

  I have a node cluster 3 ESX4.1U1 with iSCSI SAN connectivity. I have multiple VMFS LUNS mapped in the cluster, and certain RDM mapped to the guests.

  A guest, a Windows 2008 R2 VM, has a large ROW mapped. This, according to the SAN is 1.89 TB in size, and I am almost out of space. If I look at storage adapters in vCenter Configuration, it also shows that 1.89 TB, but the Windows 2008 VM shows like 1936 GB. OK, so that sounds about right.

  I want to add an another 100 GB to the LUN. I added this on the SAN, so the LUN shows now 1.99 TB. A refreshment in vCenter on each cluster node also shows the LUN now as 1.99 TB, so knowing the 2 TB LUN limit, I should be ok.

  I have re-scanned disks in the Windows 2008 VM and it shows the available extra 100 GB, so I guess I can extend the volume in free space, but this will push the volume size up to 2036 GB. I read that VMware calculates LUN size in base10, so the maximum size is 2000 GB - 512bytes. I'll have a LUN liked than that, at least in the comments.

  Thing is, at this stage, that didn't stop me doing. I have no error or warning, and the fact that the cluster sees the LUN 1.99 TB seems to imply, I should be ok.

  Before I develop the volume free space, can someone confirm if I'm having problems with this? It's quite urgent, so a quick response would be appreciated. The volume of the guest is a basic (not dynamic or GPT) disk. I don't know that the MBR in Windows volume limit is 2.19 TB, so I should be ok with this.

  Look for example at the table at the bottom of the http://kb.vmware.com/kb/1012384 (load calculation required by the snapshot files)

  André

• -This rdmp.vmdk file, but no RDM configured

  Hi all

  I just found a file of _1 - accompanied by a descriptor < servername > _1.vmdk < servername > rdmp.vmdk.

  But I'm 100% certain that I never created a RDM on this environment. Moreover, I have just three LUNS and all are storehouses of data VMFS.

  However, the file is supposed to be 90 GB in size, and I can not rename, delete, or move. I turned to the virtual machine that can be associated with him (he has the same server name), but that makes no difference. I also tried to migrate the virtual computer to another data store hoping that VMWare would fix my problem magically, but not . The file descriptor and rdmp.vmdk remain at the former location.

  The date of change of the two files is somewhare in August 2010.

  Content descriptor:

  # Disk DescriptorFile

  version = 1

  Encoding = 'UTF-8 '.

  CID = 691828e7

  parentCID = ffffffff

  createType = "vmfsPassthroughRawDeviceMap."

  # Description of the measure

  RW 195312480 VMFSRDM "< servername > _1 - rdmp.vmdk.

  # The database disk

  #DDB

  ddb.adapterType = "free".

  DDB. Geometry.sectors = "63".

  DDB. Geometry.Heads = "255".

  DDB. Geometry.Cylinders = "12157".

  DDB. UUID = "60 00 C2 95 7 b 2 c c5 fc - 00 05 21 5 d 2f f6 73 ac.

  ddb.longContentID = "dc6635ee04566420e4baad22691828e7".

  ddb.virtualHWVersion = "7".

  It seems to be a real ROW. If so, how can it be 90GB if it is just to get through. I have HP P2000 SAN and there is certainly no LUNS with a size of 90 GB. Also, as I said, the only 3 LUNS configured on the P2000 are VMFS data warehouses.

  How can I get rid of this file, or maybe know what VM it is connected and if there is no data in there?

  Oh, it's a pile of ESXi 4.1.

  For the vmkfstools command, specify "_1.vmdk" (not "_1 - rdmp.vmdk").

  Have you tried to delete the two files vmdk from the command line?

  André

• How to use an analog signal to conditionally generate a TTL (or a square function) signal?

  Hello world

  I am using PCI-6229 and try to develop a code that can generate a TTL/place function signal from only one analog entry satisfies following conditions: 1. crossing a certain value (for example, 0 V); 2 slope edge of fall. The time delay between the point of passage and newly generated signal TTL/square will be essential to my measurement, and may not exceed 1 millisecond. Any suggestion on this subject? Thank you in advance!

  You are using the measure called Excel add-in? That's what this forum is for. Otherwise, you should post to the multifunction DAQ card and speak the language you are using.

• Conditional replace Function

  Good afternoon everyone,

  I am trying to assign which I am certain is a basic replace function on certain values in the first column of a table depends on the value of the second column. So if I run the SELECT simple below I get the following:

  -SCRIPT-

  SELECT Col_name_1, Col_name_2

  Table_Name FROM

  -Results-

  Col_name_1 Col_name_2

  13                    0

  23                    0

  44                    1

  47                    1

  50                    0

  Now, say I wanted to replace the values of "Col_name_1" for negative values if the value in the same line of "Col_name_2" is 1. Which gives the following result.

  Col_name_1 Col_name_2

  13                    0

  23                    0

  -44                    1

  -47                    1

  50                    0

  
  

  , What would be the most effective way to do it. I thought using logic in the sense of if (Col_name_2 = 1), and then replace (col_name_1, '-&col_name_1') the syntax of this is obviously incorrect, I was wondering how I could produce a "function to replace conditional" which affect only certain rows in the table of results depends on the State.
  
  Thank you very much

  Charlie

  Hello

  7eb33dbf-5ba7-4248-8088-339e77b11c5e wrote:

  Hi, thanks for you far pointers. Some real examples of data. Col_name_1 was actually 'TARGKEY' and Col_name_2 'CHANGESIGN' then the digital operations to find the reverse (*-1) won't work.

  I guess that means I'm trying to add a hyphen to the TARGKEY value indicates if the value of CHANGESIGN is 1

  To clarify, yes I'm trying only to change the values in the table of results and not "up-to-date" the table of origin.

  It comes to my script.

  SELECT TARGKEY, CHANGESIGN

  OF FDM_SAB. TDATAMAP

  TARGKEY	CHANGESIGN
  P0126010	1
  P0126015	1
  P0126015	1
  P0126015	1
  P0126015	1
  P0126015	1
  P0126015	1
  P0126015	1
  P0126015	1
  1078	0
  1078	1
  1078	0
  [NONE]	0

  Once more, always post CREATE TABLE and INSERT statements for the sample data and show the exact results you want from this data.

  If targkey is a string, you can prepend a hyphen with the |   operator, like this:

  SELECT THE CHECK BOX

  WHEN changesign = 1

  THEN '-' | targkey

  Of OTHER targkey

  END AS new_targkey

  changesign

  OF tdatamap

  ;

  It is preceded by a hyphen to targkey when changesign = 1.  That is what you want, or there are a few exceptions (for example, targekey already begins with a hyphen or is null)?  If there is no special cases like this one, include examples in the sample data, results and explanations.

• OK to remove the mapping of RDM?

  I need to cold migrate some virtual machines with virtual RDM mode on new servers. I'll introduce the RDM with different numbers of LUNS on the target hosts. My co worker suggests that when you remove the ROW before the migration of the cold, you can not delete the mapping file, otherwise this will cause data corruption, so it selects the removal of the option of vm (not remove and delete).

  My understanding is the file ROW is just a mapping file and is safe to delete. My thought is that delete saves space and accelerates the migration time.

  RDM files can simply be removed without data corruption?, most vmware articles suggest they can and they're just mapping files.

  When the virtual machine allows you new hosts, a new virtual RDM will be added when the lun is presented to the new hosts.

  Yes, you can delete the ROW with removal of the VM disk option before the migration of the cold.

  It won't cause any data corruption that all data is on LUN storage.

  RDM file contain only for the LUN mapping information.

  Once you have completed the migration of VM, you can add RDM LUN to VM, just make sure that you attach Correct RDM LUN to VM.

  See this KB for more information-

  VMware KB: Switching between physical and virtual compatibility modes in ESX/ESXi, a mapping of raw data

• VMotion VMs Wit RDM

  People,

  Can you vmotion a VM with RDM LUN inside from one node to another in a cluster on the fly?

  Also, I would like to know if I put the ESXi in maintenance mode, all virtual machines including those with RDM connected gets vmotioned to other nodes in the cluster automatically

  Rahul-

  Hi Rahul

  It is stated in the Documentation that you can use with VM with RDM vSphere vMotion.

  Documentation Center of vSphere 5.5 - on Raw Device Mapping

  With RDM, you can:

  - Use vMotion to migrate virtual machines using raw LUNS.

  
  

  If you use vMotion to migrate the virtual machines with RDM, be sure to maintain Consistent ID LUN for RDM on all participating ESXi hosts.

  Considerations of RDM & limits are listed here: Library of vSphere 5.5-RDM considerations and Limitations

  FYI, links related to RDM:

  VMware KB: Microsoft Clustering on VMware vSphere: guidelines for supported configurations

  VMware KB: Difference between RDMs physical compatibility and virtual RDM compatibility

  VMware KB: Migration of virtual machines with Raw Device mapping (RDM)

  VMware KB: Frequently asked Questions on VMware vSphere 5.x for VMFS-5

  VMware KB: Cannot use snapshots or perform a backup on virtual machines configured with bus sharing

  vSphere 5.1 - VMDK versus RDM | VMware vSphere Blog - VMware Blogs

  Use RDM for practical reasons and not for Performance reasons. VMETC.com

  http://www.VMware.com/files/PDF/performance_char_vmfs_rdm.PDF

  Physical RDM for the functionality of Migration VMDK | VMware vSphere Blog - VMware Blogs

  Migration of RDM and a question for users of RDM. | VMware vSphere Blog - VMware Blogs