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 <stefanha@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
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@@ -0,0 +1,117 @@
+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