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Andy Arismendi
Asked: 2012-01-17 15:10:25 +0800 CST

VMware VM with more than 2TB of disk space

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I'm a VCP 4 so I'm aware of the configuration maximums for LUNs/RDMs/VMDKs in vSphere 4, but say I want to create a VM that has a logical drive bigger than 2TBs. The only ways I can think of doing this are:

  1. Creating the VM with multiple VMDKs each less than 2TB on different LUNs and spanning or software RAIDing them in the guest operating system.

  2. Creating a VMFS extent across multiple LUNs and creating multiple VMDKs and spanning or software RAIDing them in the guest operating system (just a slight variation of #1).

  3. Use multiple 2TB or smaller RDMs and spanning or software RAIDing them in the guest operating system.

  4. Mount an iSCSI LUN larger than 2TB from the guest operating system.

All of these methods rely on spanning/software RAIDing from the guest operating system. Is this pretty much it or are there other possibilities?

Update TomTom pointed out a 4th option.

Update 2 Tom's hardware has an interesting article about a petabyte sized storage device. They have a screenshot of it mounted via NFS in vSphere 4.1. As to JakeRobinson's suggestion with NFS, the sky is the limit with these types of datastores!

enter image description here

vmware-esxi vmware-esx vmware-vmdk vmware-vsphere

3 Answers

  1. Best Answer

    That's pretty much it in 4.x.

    vSphere 5.0 allows for pass-thru RDMs to be larger (about 60 TB), but still has the 2 TB limit in place for VMDKs and non-pass-thru RDMs. (reference). Pass-thru (physical) RDMs and non-pass-thru (virtual) RDMs are distinguished by what degree the SCSI commands are virtualized by vSphere. Pass-thru RDMs are sent all SCSI commands with the exception of the REPORT_LUN directly whereas the the non-pass-thru RDMs have all their hardware characteristics hidden and VMKernel only passes the READ and WRITE commands to the device as it is presented to the guest operating system as any other VMDK on a VMFS volume (see KB2009226).

    If you can upgrade to 5.0 and use RDMs, then great; otherwise, you're stuck gluing VMDKs or <2TB RDMs together in the guest OS with LVM or a software RAID.

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  2. Don't forget network attached storage type protocols (eg. NFS, CIFS). That is, if your SAN/NAS supports serves them up. Obviously a VM providing either of those would kinda defeat the purpose.

    Linux guests can use multiple VMDKs for an LVM, which is not exactly spanning and not exactly RAID.

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  3. You can span multiple extents. This would be at the hypervisor level, not guest OS level. The guest would be unaware.

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