Question about pci passthrough for guest (SSD passthrough) ?
I have recently added a fresh installed host on 4.4, with 3 x nvidia gpu's which have been passed through to a guest VM instance. This went very smoothly and the guest can use all 3 host GPUs. The next thing we did was to configure "local storage" so that the single guest instance can make use of faster nvme storage (100,000 iops) compared to the network iscsi storage which is rated at 35,000 iops. The caveat with local storage is that I can only use the remaining free space in /var/ for disk images. The result is the 1TB SSD has around 700GB remaining free space. So I was wondering about simply passing through the nvme ssd (PCI) to the guest, so the guest can utilise the fill SSD. Are there any "gotcha's" with doing this other than the usual gpu passthrough ones? Also my apologies if this is duplicated. I originally asked this [1] a couple of days ago but I am not sure what happened. Kind regards, Tony Pearce [1] Question about pci pass-thru - Users - Ovirt List Archives <https://lists.ovirt.org/archives/list/users@ovirt.org/thread/BN7XHUN2DP6RQGE2MQDBTDSMSXW34PTP/>
You won't be able to migrate the VM from the host, but it should work. Best Regards,Strahil Nikolov On Wed, Aug 4, 2021 at 12:49, Tony Pearce<tonyppe@gmail.com> wrote: I have recently added a fresh installed host on 4.4, with 3 x nvidia gpu's which have been passed through to a guest VM instance. This went very smoothly and the guest can use all 3 host GPUs. The next thing we did was to configure "local storage" so that the single guest instance can make use of faster nvme storage (100,000 iops) compared to the network iscsi storage which is rated at 35,000 iops. The caveat with local storage is that I can only use the remaining free space in /var/ for disk images. The result is the 1TB SSD has around 700GB remaining free space. So I was wondering about simply passing through the nvme ssd (PCI) to the guest, so the guest can utilise the fill SSD. Are there any "gotcha's" with doing this other than the usual gpu passthrough ones? Also my apologies if this is duplicated. I originally asked this [1] a couple of days ago but I am not sure what happened. Kind regards, Tony Pearce [1] Question about pci pass-thru - Users - Ovirt List Archives _______________________________________________ Users mailing list -- users@ovirt.org To unsubscribe send an email to users-leave@ovirt.org Privacy Statement: https://www.ovirt.org/privacy-policy.html oVirt Code of Conduct: https://www.ovirt.org/community/about/community-guidelines/ List Archives: https://lists.ovirt.org/archives/list/users@ovirt.org/message/WJKUWVIJCZT7LB...
The caveat with local storage is that I can only use the remaining free space in /var/ for disk images. The result is the 1TB SSD has around 700GB remaining free space.
So I was wondering about simply passing through the nvme ssd (PCI) to the guest, so the guest can utilise the fill SSD.
Are there any "gotcha's" with doing this other than the usual gpu passthrough ones?
The caveat is that you cannot pass through a partial SSD, only a whole device. And as a matter of fact, I'd say you can only pass through entire PCI(e) devices, so traditional SCSI/SATA disks might not work individually, you'd have to pass through the entire controller. Effectively you'd "unplug" the NVMe from the host and plug it into the guest and if that wasn't stopped by some sanity check, neither system would continue to run for long, if that is your boot device (or the disk is used otherwise). I know 3x more IOPS sound attractive, but is your workload really that disk bound? Perhaps you'll need to think about some distributed memory cache.
participants (3)
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Strahil Nikolov -
Thomas Hoberg -
Tony Pearce