> Op 21 januari 2017 om 16:15 schreef Syed Ahmed <sah...@cloudops.com>: > > > Wido, > > Were you thinking of adding this as a global setting? I can see why it will > be useful. I'm happy to review any ideas you might have around this. >
Well, not really. We don't have any structure for this in place right now to define what type of driver/disk we present to a guest. See my answer below. > Thanks, > -Syed > On Sat, Jan 21, 2017 at 04:46 Laszlo Hornyak <laszlo.horn...@gmail.com> > wrote: > > > Hi Wido, > > > > If I understand correctly from the documentation and your examples, virtio > > provides virtio interface to the guest while virtio-scsi provides scsi > > interface, therefore an IaaS service should not replace it without user > > request / approval. It would be probably better to let the user set what > > kind of IO interface the VM needs. > > You'd say, but we already do those. Some Operating Systems get a IDE disk, others a SCSI disk and when Linux guest support it according to our database we use VirtIO. CloudStack has no way of telling how to present a volume to a guest. I think it would be a bit to much to just make that configurable. That would mean extra database entries, API calls. A bit overkill imho in this case. VirtIO SCSI is supported by all Linux distributions for a very long time. Wido > > Best regards, > > Laszlo > > > > On Fri, Jan 20, 2017 at 10:21 PM, Wido den Hollander <w...@widodh.nl> > > wrote: > > > > > Hi, > > > > > > VirtIO SCSI [0] has been supported a while now by Linux and all kernels, > > > but inside CloudStack we are not using it. There is a issue for this [1]. > > > > > > It would bring more (theoretical) performance to VMs, but one of the > > > motivators (for me) is that we can support TRIM/DISCARD [2]. > > > > > > This would allow for RBD images on Ceph to shrink, but it can also give > > > back free space on QCOW2 images if quests run fstrim. Something all > > modern > > > distributions all do weekly in a CRON. > > > > > > Now, it is simple to swap VirtIO for VirtIO SCSI. This would however mean > > > that disks inside VMs are then called /dev/sdX instead of /dev/vdX. > > > > > > For GRUB and such this is no problems. This usually work on UUIDs and/or > > > labels, but for static mounts on /dev/vdb1 for example things break. > > > > > > We currently don't have any configuration method on how we want to > > present > > > a disk to a guest, so when attaching a volume we can't say that we want > > to > > > use a different driver. If we think that a Operating System supports > > VirtIO > > > we use that driver in KVM. > > > > > > Any suggestion on how to add VirtIO SCSI support? > > > > > > Wido > > > > > > > > > [0]: http://wiki.qemu.org/Features/VirtioSCSI > > > [1]: https://issues.apache.org/jira/browse/CLOUDSTACK-8239 > > > [2]: https://issues.apache.org/jira/browse/CLOUDSTACK-8104 > > > > > > > > > > > -- > > > > EOF > >
