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Subject: Re: Re: [virtio-comment] About adding a new device type virtio-nvme
On Tue, Jan 17, 2023 at 10:04:07AM +0800, äèä wrote: > On Wed, 11 Jan 2023 10:16:55 -0500, Stefan wrote: > > > >>On Wed, Jan 11, 2023 at 11:21:35AM +0800, äèä wrote: > >> As we know, nvme has more features than virtio-blk. For example, with the development of virtualization IO offloading to hardware, virtio-blk and NVME-OF offloading to hardware >are developing rapidly. So if virtio and nvme are combined into Virtio-NvMe, Is it necessary to add a device type Virtio-NvMe ? > > > >  > > > > >Hi, > >In theory, yes, virtio-nvme can be done. The question is why do it? > > > > >NVMe already provides a PCI hardware spec for software and hardware > >implementations to follow. An NVMe PCI device can be exposed to the > >guest and modern operating systems recognize it without requiring new > >drivers. > > > >The value of VIRTIO here is probably in the deep integration into the > >virtualization stack with vDPA, vhost, etc. A virtio-nvme device can use > >all these things whereas a PCI device needs to do everything from > >scratch. > > > The NVME technology and ecosystem are complete. However, in virtualization scenarios, NVME devices can only use PCIe pass-through . When NVME and virtio combine to connect to the vDPA ecosystem, live migration is supported. > > > >Let's not forget that virtio-blk is widely used and new commands are > >being added as needed. Which NVMe features are you missing in > >virtio-blk? > > With the introduction of the concept of DPU, a large number of vendors are offloading virtual devices to hardware. The back-end of Virtio-blk does not support remote storage. Therefore, Virtio-Nvme-of can well combine the advantages of remote storage and virtio live migration virtio-blk is just a storage interface, whether that storage is local or remote is up to the device implementation. The block device could be located on Ceph, NFS, etc. Each virtio-blk device is a single block device. There is no standardized management protocol in virtio-blk for connecting to remote block devices. I'm aware of hardware virtio-blk devices that connect to remote storage. Configuration is performed through an out-of-band management interface. Maybe when you say virtio-blk doesn't support remote storage this is what you mean? Stefan
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