1.1.1. VSI OpenVMS Does Not Support Thin-Provisioned Volumes

[mgdaniel]

An interesting question on behalf...

https://docs.vmssoftware.com/vsi-openvm ... ase-notes/

> With regard to the release notes, do you understand this restriction?
>
> 1.1.1. VSI OpenVMS Does Not Support Thin-Provisioned Volumes on
> Any Architecture
>
> I understand "Thin provisoning" to be that when an OpenVMS tries to
> define a disk with a certain size, that the virtualizing platform does
> not initially reserve all the space defined, but only for the blocks
> that are occupied. When the space grows the virtualization SW will map
> more physical storage.
>
> With "thick provisioning" all the physical space is pre-allocated,
> whether an Operating System uses it or not.
>
> What does an Operating System have to do to be able to support "Thin
> provisioning"?
>
> Does a virtualizing environment VMware/KVM not act like an intelligent
> storage solution?
> ie. it is all transparent for the Operating System?

[mgdaniel]

HPE implemented the trimming part of thin provisioning in response to a customer request; that support appeared in a patch to HPE VMS V8.4.

The implementation was not good; the performance was so bad the customer never actually used the feature.

I took a look at the work HPE did, and decided we (VSI) should not accept that change in the VSI sources.

It was a pretty large change, in that it touched not only the SCSI class driver DKDRIVER, but also the code that implements MOUNT, INIT, DELETE, several SHOW commands, $GETDVI, the STARLET and LIB libraries, and a few other places that I cannot remember off the top of my head.

-- Rob

Again, thank you Rob. Authoritative is always (more) useful than speculation.

[imiller]

Thanks Rob - I'd guessed something like that.