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Subject: Re: Re: [virtio-comment] About adding a new device type virtio-nvme
On Tue, 17 Jan 2023 11:01:37 -0500, Stefan wrote: >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? Yes, virtio-blk devices offlaod to hardware, For example, DPU and SmartNIC. So, compare virtio-nvme with virtio-blk and NVME. Stefan
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