On 19/01/2021 15.15, Stefan Hajnoczi wrote:
The second post in the storage series covers virtio-blk and virtio-scsi. It compares the two and offers recommendations that users and tools using QEMU can use as a starting point. Graphs are included comparing the performance of various options.Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com> --- v3: * Mention guest drivers for other operation systems [Thomas] * Reorder virtio-blk/virtio-scsi key points [Thomas] * Mention that virtio-blk is limited to disk emulation and doesn't handle CD-ROM drivers, for example [Thomas] v2: * Mention default storage controllers for non-x86 [danpb] * Remove statement about read-only ISO virtio-blk devices, both Rich Jones and Daniel Berrange commented about this at different times so I decided to drop it completely [danpb] * Clarify PCI slot limits and multi-function discussion for virtio-blk [danpb] * Mention multiple virtio-scsi devices for NUMA tuning and that emulated LUNs can be HDDs or CD-ROMs [danpb] --- ...021-01-19-virtio-blk-scsi-configuration.md | 117 ++++++++++++++++++ screenshots/2020-09-15-scsi-devices.svg | 1 + screenshots/2020-09-15-virtio-blk-vs-scsi.svg | 1 + 3 files changed, 119 insertions(+) create mode 100644 _posts/2021-01-19-virtio-blk-scsi-configuration.md create mode 100644 screenshots/2020-09-15-scsi-devices.svg create mode 100644 screenshots/2020-09-15-virtio-blk-vs-scsi.svg diff --git a/_posts/2021-01-19-virtio-blk-scsi-configuration.md b/_posts/2021-01-19-virtio-blk-scsi-configuration.md new file mode 100644 index 0000000..a9c7a35 --- /dev/null +++ b/_posts/2021-01-19-virtio-blk-scsi-configuration.md @@ -0,0 +1,117 @@
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+Virtual machines that require access to many disks can hit limits based on +availability of PCI slots, which are under contention with other devices +exposed to the guest, such as NICs. For example a typical i440fx machine type +default configuration allows for about 28 disks. It is possible to use +multi-function devices to pack multiple virtio-blk devies into a single PCI
Thanks! I've replaced "devies" with "devices" and pushed it to the repo now. Thomas
