It may be a bit of a surprise that virtualization with vSphere has not meant that every dimension of mobility has increased. We see more ability to move a VM from one physical server to another with VMotion and the ability to move from one piece of storage to another with Storage VMotion. The thing is that all of this mobility assumes that the source and destination are VMware based environments. There has always been an issue with data mobility between VMware and non-VMware workloads.
Mainly the issue is that VM data lives in vmdk files on datastores, those files and datastores are only accessible to ESXi servers. Datastores are either VMFS formatted LUNs or NFS shares. Only an ESXi server can read VMFS formatted LUNs an can contain multiple VMs, and multiple hard disks for each VM. A datastore on an NFS share is readable by a range of different operating systems, but only ESXi can provide access to the VMs disks on those shares. A VM encapsulated on an NFS or VMFS datastore is only useful to a VMware hypervisor. What if I want a copy of that VM or its data on a physical server? Or another hypervisor? Or a public cloud? Or if I want to start on another platform and get a copy on vSphere? The conventional approach is to go inside the VM, use an in-guest application to copy over the guest network to another location. This is entirely workable, but not necessarily the most efficient method.
VMware has a recent feature allows far more mobility than was previously possible. VVols is often viewed as VMware fixing some limitations that they created with storage. The reality is that VVols unlocks VM data and enables data portability. As far as the storage array is concerned, each VVol is just a LUN. The Data-VVols are where the VM stores it’s data and are formatted by the VM using native partitioning and formatting. Since the data VVol is just a LUN formatted by a guest OS, it is readable by anything that can read that formatting. A Data-VVol can be cloned and presented to a physical server which will see the native formatting, not a VMware specific format. Equally a LUN that has been formatted by a physical server can be cloned into a Data-VVol and made available to a VM. This is a little like the flexibility of a VMware Raw Device Mapping (RDM), without all of the weird special handling that RDMs required.
Disclosure: I attended Pure Storage’s Accelerate conference as their guest, they provided travel and accommodation as well as some hospitality. Pure Storage did not commission this post nor did they have any control over the content, or even know it was being written before it was posted.
At Pure Accelerate I chatted with Cody Hosterman about the VVols portability demonstration that he showed during the conference. He started with a SQL server VM on vSphere, the disks containing the database files were on a Data-VVol. Using native Pure commands, he was able to clone that VVol to a new LUN and present it to a Hyper-V host. A SQL server VM on that Hyper-V host was able to mount the data LUN and access the database within. The LUN could have started life attached to a physical server or the Hyper-V host; it made no difference. Cody was showing cloning of the LUN to get a copy of a production database into a development environment without any reformatting. He could equally have talked about a migration strategy where the LUN was removed from one platform and presented to another, without being copied. This no-copy data migration could be a significant part of migration between virtualization platforms, even onto or off a virtual platform. An exciting functionality that Cody talked about was using the ability to clone a Pure LUN to a compressed and deduplicated AWS S3 object. That S3 object can then be hydrated into a LUN on AWS EBS and attached to an EC2 instance, to get that SQL database into an AWS based development or reporting system. Promoting an S3 object that is a storage snapshot into an EBS volume does require a helper EC2 instance to do the rehydration, this is a standard issue on AWS.
VVols may initially look like more VMware magic that binds customers more tightly to vSphere. The reality is that VVols enables far more data mobility than using VMFS or NFS datastores.
© 2018, Alastair. All rights reserved.
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