A new version of the VMFS Technical Overview and Best Practices white paper is now available. It has been updated for vSphere 5.x & VMFS5. You can download the paper from the VMware Technical Resources web site here. This new paper has been updated with VMFS5 limits, and also includes discussions around interoperability with newer vSphere features. It also has updated information around when and where to use Raw Device Mappings (RDMs), a feature which has seens it requirements change over the years.
The paper has been maintained by a number of technical marketing personnel over the years. We hope you find this latest version useful.
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My only comment on the white paper is on page 11, “Why use RDM” section. It seems to miss that flat.vmdk’s have a 2TB limit so another reason to use RDM is for vdisks > 2TB.
Carl L.
Hi Carl,
I’m not sure that limit would drive you to use RDMs. VMs can have multiple VMDKs presented to it. I discuss this in the following blog post: http://blogs.vmware.com/vsphere/2012/01/how-much-storage-can-i-present-to-a-virtual-machine.html
We work around the 2TB VMDK limit using the disk management tools built into the VMware guest’s Widows or Linux operating system. I can only speak of Linux Volume Management (LVM) in depth. LVM permits aggregating and managing multiple VMDK block devices easily and most importantly without downing applications. This includes migrating, increasing and reducing storage allocated and presented to the Linux OS. If you avoid any legacy DOS partitioning a whole new world of possibilities presents itself. The 4TB limit in VMFS 5 is a welcome change and huge improvement, but we are eager for 16 TB already. The incompatibility with VMX 7 and earlier is a challenge, but not insurmountable.
Hi Cormac
We have a request to provision a 5Tb VM (we have never provisioned a vmdk over 250Gb before) which is fine we can use 3 vmdk’s and present it to the OS. Do you have any preferences or advice on the best way to backup VM’s this big.
Thanks
Glenn
Glenn, please have a look at our VDPA product which was just announced – http://blogs.vmware.com/vsphere/2013/02/vmware-announces-vdpa.html. If this doesn’t meet you needs, we have various partners in the backup space who can help you with this.