Sharing Vhd Between Vms
Key Deployment Scenarios. Using a shared virtual hard disk is ideal for many workloads. Scenario 1: Hyper-V failover cluster using Cluster Shared Volumes (CSV) on block-level storage. In this scenario, all virtual machine files, including the shared VHDX files are stored on a CSV that is configured as shared storage for a Hyper-V failover cluster. Aug 29, 2008 One of the great features in Hyper-V is the ability to share a common base (OS) image between multiple Virtual Machines. This would allow you, for example, to create a single Windows Server 2008 OS image and base several virtual servers on that image without duplicating or copying any data.
Recently, in working with a client with many different lab environments, there arose the need to copy backups from one lab and restore into a number of other labs. The DB in question was a DB that was around 250 GB. Copying via the network between labs was going to be a nightmare both in terms of performance and in terms of how the lab environments were segregated between the various SQL DBs. Instead of utilizing the network to copy the SQL DB, I had an idea to instead use a shared VMDK between the various lab hosts and allow all the VMs needed to be able to see the and then copy the data from this shared VMDK between the VMs.
Let’s take a look at how to Share VMDK Data Between VMs Multi-Writer Disk Without Cluster File System to take a look at a bit of a hack of the technology to allow using this approach without running a cluster file system between VMs. Sharing Data with Multi-Writer Disks Use CasesI have already alluded to the potential use cases of a multi-writer disk shared between servers. Reading and writing data to disk and sharing that data between multiple VMs means you are saving the step of having to duplicate the data by having to copy it across a network and store it on the target VM.This is especially helpful if you have a large file or large amount of data you need to copy from one VM to another. The data is simply “local” to the VM if you are using a shared multi-writer disk in VMware.
This means you only have to write data once. Additionally, there can be network constraints or complexities between VMs in an environment such as between labs that can be a challenge to copying data in a timely and efficient manner between VMs that may exist in different lab environments.There is a challenge however with multi-writer VMDKs when looking to use them to share data between VMs in that you need to have a cluster aware file system to be able to simultaneously access the data between various VMs. In the Windows world, this would be using Windows Failover Cluster to negotiate and allow reading and writing between the cluster hosts to the same volume.In my case, I didn’t need or want to configure a cluster between the VMs in question. I simply wanted to quicky be able to copy and access data between VMs without the time needed to copy across the network, and have the double write penalty of copying to a local disk, then copying across a network to another disk, and then reading that data into the VM. In my case this was a SQL backup. VMware Multi-Writer VMDK Requirements and ConsiderationsThe following requirements are found in the online doc from VMware. What are those ones to note?.
Sharing Vhd Between Vms Mac
Cluster-aware file systems to avoid corruption. When using the multiwriter mode, the virtual disk must be eager-zeroed thick (EZT). When creating an EZT disk on vSAN, the disk is not zeroed automatically.
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If zeroing is required, use the vmkfstools -wcommand to zero-out all blocks. For more information, see, “Powering on the virtual machine fails with the error: Thin/TBZ disks cannot be opened in multiwriter mode.”. Shared VMDKs need not be set to independent persistent mode for the multiwriter attributeIf you notice the first mention is a cluster-aware file system. This is standard protection for a good reason.
Vhd Sets Vs Shared Vhdx
If you have non cluster aware hosts trying to access (read/write) to the same files, corruption is a good possibility and is probably likely.Let’s look at a way with Windows Server you can “cheat” this so to speak if you don’t have a cluster configuration such as Windows Failover Cluster services running between VMs. Share VMDK Data Between VMs Multi-Writer Disk Without Cluster File SystemLet’s first look at how to create a multi-writer VMDK to an existing virtual machine.
The first thing you need to do is add an additional SCSI Controller for use with the multi-writer VMDKs. I have’t tested this but I don’t think this is absolutely required, but recommended. The added folder on the source host is now visible on the target serverYou are beginning to see the process to use multi-writer VMDKs for a non-Cluster configuration. Of course, this is not a supported use of this functionality.