[SOLVED] qemu, virtio, difference between viostor and vioscsi

atelszewski.versades · 09-21-2015, 04:23 AM

Hi,

I'm struggling to find out what is the difference between viostor and vioscsi.
I know that viostor allows me to pass file to be seen as SCSI disk in the guest, but I have no clue what the vioscsi is for.

Could somebody explain please?

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Best regards,
Andrzej Telszewski

dyasny · 09-21-2015, 07:37 AM

There are two virtio block devices available. viostor is the driver for virtio_blk, a very basic block device that only supports a small number of scsi commands, but also has a small overhead and very fast. For a simple VM disk it is all you will ever require. the other device is virtio_scsi, with the driver vioscsi, it supports the complete scsi protocol, so you do do things like windows clusters over such devices.

for your particular use case, run both, check which performs best under your specific workloads and choose.

atelszewski.versades · 09-21-2015, 08:02 AM

Hi,

Thanks for the reply, basically that's everything I needed to know.

Does it make sense to try vioscsi (now I'm using viostor), if I have just a simple qemu machine with no "clusters", etc.?
Since viostor is simpler (I guess there's less abstraction, e.g. function calls), I guess this should be my choice.
Or is it only possible to know by trying them both?

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Best regards,
Andrzej Telszewski

dyasny · 09-21-2015, 10:13 AM

There are some additional differences in the way these two devices are implemented, some workloads might turn out to be faster on virtio_scsi than on virtio_blk, so the answer is - try it and choose for yourself

atelszewski.versades · 09-23-2015, 02:28 AM

Hi,

Thanks for the hints. As of now I'm gonna skip the tests.
Basically I'm running Windows 7 to work with some Windows-only applications, but all the files are hosted on the Linux host through Samba, so there shouldn't be any significant I/O when it comes to the virtualized disk.

Thanks for the help!

--
Best regards,
Andrzej Telszewski