Convert a virtual disk vmdk in a physical disk and vice versa. Distributed locking on an rdm makes it safe to use a shared raw lun without losing data when two virtual machines on different servers try to access the same lun. This is also the first time weve mapped a raw lun to esxi like this and wt veeam backup, hence why i thought they were related along with veeam seeing the vm as having 50gb total size, and 30gb processed size. The results of this will produce a vm with vmdk disks on vmfs. As we discussed in the earlier post, there are two types of rdm disks virtual compatibility rdm and physical compatibility rdm. In short it means actually data is written on the disk. One of the drives on the server is a raw mapped lun. Well, apparently, this case is not unique, so i decided to share my experience in todays. For details about rdm, see the vsphere storage documentation. Makes it possible to use vmfs distributed locking for raw scsi devices. The rdm contains metadata for managing and redirecting disk access to the physical device. In this article, we will find an easy solution to map the virtual machine disks to.
After that, bypassing the mapping file, reading, and writing goes directly to the lun. Moving an existing rdm from one virtual machine to another some steps are required to avoid data loss and to keep the disk configuration. Feb 19, 2007 it rdm not raw lun is referred in the virtual machine configuration. Converting rdms to vmfs envision technology advisors blog. Basically i require it to convert because, i was not going to use microsoft clustering anymore, also i was planning to change backend storage due to end of life. Convert iscsi mapped disk to vmware vmdk solutions. You navigate to the vm to find the rdm in question but are faced with this so which disk needs to be expanded. Some vsphere administrators utilize a storage feature called raw device mapping or rdm. When you map a lun to vmfs, it creates a file with extension vmdk, which points to raw lun. The vmware team has published a lot of evidence in the past that the difference is very minor, in fact difficult to measure accurately and probably unperceivable to. Solved convert raw disk to vmdk virtualization spiceworks. Traditionally, a vm disk or vmdk consists of storage space carved out of the underlying.
Removing a raw mapped lun from a vmware vm solutions. Power on to verify all is running, and new drives are mapped to the correct drive letters or mount points. Large vmdk vs iscsi attached san storage just wondering if anyone has any input on choosing to have a 56 tb. Take a look at the 11 differences between rdm physical vs virtual. Vmfs virtual file based disk vmdk or a raw device mapping rdm. Veeam backup error, possibly mapped raw lun related. Rdms can be presented in either virtual compatibility mode or rdmv or physical compatibility mode or rdmp. Powercli script to identify which vm is using an rdm lun identified by the naaid of the lun. Jan 22, 2018 vmware rdm raw device mapping is a mapping file that provides direct access to a lun on an iscsi or fibre channel storage system for a virtual machine. Is it better to present the pool of drives as a iscsi target to a windows fileserver directly and store files that way or connect it to a exsi server and store the data within vmdk disks. Feb 23, 2009 this tip defines virtual disks, explains the three main types of virtual disks and makes recommendations on when to use each type. If you want to do faster p2vs you can just convert the c. A vmware virtual hard disk can be made up one or multiple vmdk files. Run fewer servers and reduce capital and operating costs using vmware vsphere to build a cloud computing infrastructure.
Rdms can be described in terms such as mapping a raw device into a datastore, mapping a system lun, or mapping a disk file to a physical disk. Use an rdm with virtual machine clusters that require access to the same raw lun for failover scenarios. Jan 12, 2014 mapping windows drives to rdms in vmware esxesxi january 12, 2014 by japinator it can be confusing when trying to identify the rdm that correlates to a windows drive. Easily convert netapp luns to vhdx or vmdk files its. Jul 17, 2015 recently i was tasked with converting iscsi connected disks on windows servers to a new san. The original mapped lun is left alone after the migration completes, and can be removed as necessary to reclaim space.
Actually, it was my mistake reading the converter output. The mapped device appears to the guest operating system exactly the same as a virtual disk file in a vmfs volume. The rdm allows a virtual machine to directly access and use the storage device. So if you dont delete the vmdk from the disk you wouldnt find the raw lun when you attempt to reattach it much later. There is a misunderstanding that rdms offer greater performance compared to vmdk s on. Pass through disk recommendations for vmware hyperconverged.
You can carve that up into as many zfs filesystems as youd like. Convert raw mapped lun from a virtual to physical or vice versa. If the source vmdk is hosted on a lun, it must be an ntfs formatted lun mounted to the host running this commandlet. When you map a lun to a vmfs volume, vcenter server creates a raw device mapping rdm file that points to the raw lun. Jun 30, 2017 i found an article that states we can convert a vmdk file into a raw mapped drive, and this is the process we are looking to follow. Solved iscsi lun which is mounted from within the vm. Powercli script to identify which vm is using an rdm lun. With rdm, vmdk files are only pointers to a vms disk data, while on vmfs the files also hold. Also note, that the vmdk cannot have any vmdk snapshot disks associated with it. A physical connected rdm cannot be converted online to a vmdk. That includes zvols volumes that can be exported as block devices a major point of using zfs is to give you maximum storage flexibility for example, i have the following set of zfs filesystems, where the first four listed are nfs mounts exported. Now if your doing this for anything else, i do have a patented double lun swapparo system to do this with less than 5 minutes of downtime, and no robocopyfile copy. As it turned out, this was a pretty easy task as we were on vsphere 5 and i had some free storage on the san to deploy a new lun for the server. Creatingadding a raw device mapping rdm to a virtual machine.
Before that we need to convert the physical rdm to a virtual rdm. It rdm not raw lun is referred in the virtual machine configuration. This mapping file, which has a vmdk extension, points to the raw device rdm file lock is translated to scsi reservation on the lun utilities like admsnap and admhost, installed on the virtual machines, can directly access the. Aug 25, 20 if you want to do faster p2vs you can just convert the c. Each drive can be either a virtual disk or a raw device mapping. Start adding lun as a vrdm, stop right before you hit apply. Converting iscsi targets in windows to vmdk mikails blog. Colloquially, this is what is often referred to as a virtual disk vmdk. Please note, you cannot convert a lun to a target vhd directly on the volume figure 3 the target vhd has to be within a lun. Rescan your hbas and check under storage adapters to ensure the cluster can see the lun. Add an rdm disk to a virtual machine in the vsphere client. Apr 26, 20 the original mapped lun is left alone after the migration completes, and can be removed as necessary to reclaim space.
A raw disk mapping rdm can be used to present a lun directly to a virtual machine from a san. An rdm is raw lun that is presented directly to a vm instead of creating a traditional virtual disk on a vmfs datastore. Encapsulating disk information in a file allows vcenter server to lock the lun so that only one virtual machine can write to it at a time. There are two types of rdm disks virtual compatibility rdm and physical compatibility rdm. Jul 03, 2014 vmdk maximizes vsphere storage tooling. Right now we have two file share luns 2tb and 5tb, that will be cleaned up and converted into a new sharepoint infrastructure that we are implementing. Vmware raw device mappingrdm lets design, implement and. When creating the rdm pointer file, should we be using virtual or physical compatibility mode in vmware. Raw device mapping rdm is one way to pass a raw disk device directly through from the disk controller to the softnas cloud vm in vmware. This mapping file, which has a vmdk extension, points to the raw device rdm file lock is translated to scsi reservation on the lun utilities like admsnap and admhost, installed on the virtual machines, can directly access the raw devicepartition. Take a look at the 11 differences between rdm physical vs virtual compatibility mode. Distributed locking on a raw device mapping makes it safe to use a shared raw lun without losing data when two virtual machines on different servers access the same lun. If your san management software integrates with vsphere to auto mount the lun as a datastore, skip that step.
If you are moving sql server or oracle data from rdm to vmdk, please use the advanced tab in the migration wizard to specify thick provisioned. Our infrastructure is setup in a very traditional manor ie all the san storage is presented to the vms as luns using the iscsi initiator within the vms. Mapping of the lun to esxi hosts is done as per normal. Jan 09, 20 it seems the debate between using a vmdk on vmfs or an rdm still rages when it comes to the question which one is better for performance.
How to convert rdm to vmdk the ultimate guide vmware arena. To import a virtual disk into a raw lun for use with an rdm in esxiesx 4. It will list them as mapped raw lun in the vm configuration. I would like to remove this raw lun from the server and make it available to the sans for creating a new virtual disk. The question often comes up, when should i use raw device mappings rdms instead of traditional vmfsvmdk virtual disks. With this migration it was decided that we should convert the disks to native esxi vmdk format. The question often comes up, when should i use raw device mappings rdms instead of traditional vmfs vmdk virtual disks.
In practice, this means that a virtual machines rdm disk maps directly to a chunk of storage, a lun. Provides somewhat less vsphere storage tooling than vmdk. These vmdks can be added to your virtual machine using the vsphere client in the normal way just tell it that they are existing virtual disks and it works out the rest. High availability ha and drs in esx vmware vmfs vs rdm raw device mapping posted by craig on august 22nd, 2008 in virtualization 3 comments. However, we can see hard disk 2 is mapped to a physical lun at the bottom of the screen shot you will not see that with a regular vmdk file. Now if your doing this for anything else, i do have a patented doublelun swapparo system to do this with less than 5 minutes of downtime, and no robocopyfile copy.
Vmdk file is the virtual disk image file created by vmware software. This tip defines virtual disks, explains the three main types of virtual disks and makes recommendations on when to use each type. Done this for some very low downtime migrations of dbs and file servers with a ton of data. Convert iscsi mapped disk to vmware vmdk solutions experts.
A virtual rdm behaves the same as a vmdk file based disk except that it is backed by raw block storage. Cleaning up the mapped rdm luns in the guest operating system. There is a misunderstanding that rdms offer greater performance. As we already discussed many times, vmware rdm raw device mapping is a mapping file that provides direct access to a lun on the fiber channel storage system for a virtual machine. It can be confusing when trying to identify the rdm that correlates to a windows drive.
Vmware virtual machines comprise a set of files in typically one of two given formats. Just make sure you attach them to a scsi controller of the same type above. Write down the drive letter of the disk in the guest os. Virtual compatibility mode allows a mapping to act exactly like a virtual disk file. Creatingadding a raw device mapping rdm to a virtual. All the files have been removed from this drive and it is no longer needed for the server. Vmware rdm raw device mapping is a mapping file that provides direct access to a lun on an iscsi or fibre channel storage system for a virtual machine. File permissions raw device mapping makes file permissions possible. Raw device mapping or rdm involves more configuration and ongoing operational overhead compared to vmfs. Also, with direct access, physicaltovirtual conversion becomes possible without migrating a massive lun to vmdk. Mark achtemichuk over at vmware published a great article the other day on the use of vmdks virtual machine disk versus rdms in vmware vsphere 5. Raw device any scsi device accessed via a mapping file. As a result, it merges vmfs manageability with raw device access. Storage admins used to match luns to physical servers, but thats all changed.
To open vmdk file, please follow the steps, click the open button on toolbar or choose file open menu to open vmdk file. How to create vmware rdm physical compatibility disk. Cleaning up the mapped rdm luns in the guest operating. Both formats enable you to access the virtual machines disk, but they differ in approach to storage, and vmware recommends vmfs for the vast majority of vms. The answer for this usually is, always use vmfs unless you fit into specific use cases. Rather than creating a virtual disk vmdk on a lun, which is generally shared with other vms and virtual disks.
It is not possible to storagevmotion the iscsi disks without doing some work first see below as the hypervisor does not see continue reading converting iscsi targets in. To enable your vms to talk directly to lun, you need a raw device mapping file. Find out how in this guide to the basics of vm storage. Attach newly created vmdks to vm, ideally choosing a device node of anything other than 0. It makes it interesting later on down the road if youre attempting the luntovmdk conversion and ill address how to get around that later in this article. The rdm allows a virtual machine to directly access and use the storage device and before proceeding with the move, the virtual machine where the rdm is currently attached must be shut down. One of those 5 disks is mapped via esxi iscsi initiator and has the same capacity as osmounted iscsi volume, so at first sight i thought it is the same iscsi volume, somehow seen by converter. You can also use a storage vmotion operation to perform the same migration task.
There are two compatibility modes for raw device mappings, virtual and physical. Vmware vsphere physical and virtual rdm bretts it blog. Mapping file a vmfs file containing metadata used to map and manage a raw device. I logged into the windows virtual machine, configured the newlyadded storage, formatted the volume with ntfs and made it the r. Each drive is a file on a file system nfs or vmfs that is presented to a vm to look like a standalone scsi volume. Finally, we have the vmdk file based disk, which is a fully virtualized storage device. The reasons for doing this should purley be for functional and management reasons, not performance. Vmware raw device mappingrdm lets design, implement. Once storage vmotion is completed, virtual rdm disk will be converted to vmdk. The file gives you some of the advantages of direct access to a physical device while keeping some advantages of a virtual disk in vmfs. Cleaning up the mapped rdm luns in the guest operating system and esx server. The trick here is to put the rdm in virtual mode and use storage vmotion to migrate it to another lun. Raw device mapping rdm is a mapping file that provides direct access to a lun on an iscsi or fibre channel storage system for a virtual.
Vmware raw device mapping and file recovery diskinternals. We have a sas box with 24 drives connected to openindiana server configured as a pool of 11 mirrored drives with two spares. When a vm is configured to use a rdm, the selected lun is dedicated. This just a file, which contains information about raw lun and it is locked by virtual center so that vm can write to lun. In my previous article i shown adding and sharing rdm disk to multiple vms in vmware step by step, i received one related task to convert virtual machine rdm raw device mapping hard disk to vmdk disk. I found an article that states we can convert a vmdk file into a raw mapped drive, and this is the process we are looking to follow.
It seems the debate between using a vmdk on vmfs or an rdm still rages when it comes to the question which one is better for performance. How to convert rdm disk raw device mapping to vmdk. The setup is similar to that of a virtual machine cluster that accesses the same virtual disk file, but an rdm replaces the virtual disk file. An rdm is a mapping file in a separate vmfs volume that acts as a proxy for a raw physical storage device. Theres no supported topology that allows you to convert a source vmdk hosted on a vmfs formatted lun.
It is not possible to storagevmotion the iscsi disks without doing some work first see below as the hypervisor does not see continue reading converting iscsi targets in windows to vmdk. Jul 17, 2015 however, we can see hard disk 2 is mapped to a physical lun at the bottom of the screen shot you will not see that with a regular vmdk file. Currently a netapp filer but plans are to go nimble. Mapping file a vmfs file containing metadata used to map and manage a. Raw mapped lun vs vmdk files williambishop dec 4, 2008 5.
Raw device mapping makes it possible to use vmfs distributed locking for raw scsi devices. Easily convert netapp luns to vhdx or vmdk files its magic. Currently a netapp filer but plans are to go nimble storage with full ssd. Doing some quick searching in the vmware kb, i found vmware articles 1005937 had a powercli script which showed the size of the rdm and the full path of the rdm. It could be an interesting tool for doing forensics examinations on compromised boxes when all you have is a dd dump of the drive to work on, it allows you to. To give you some context, lets assume you receive a request to increase the k. If you are using a raw disk in virtual mode, you can realize the benefits of vmfs such as advanced file locking for data protection and snapshots for streamlining development processes. Older vmware documentation indicates rdm is not supported by locallyattached devices, which is no longer the case. Vmware virtualization rdm to vmdk migration house of. When you open the lun for virtual machine access, the mapping file is read and thus receives a link to the raw lun. You will find the entire rdm mapped entry as mapped raw lun for every rdm entry. Recently i was tasked with converting iscsi connected disks on windows servers to a new san.
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