[ovirt-users] Strange drive performance over 10Gb

[Wesley Stewart]

I was curious if anyone else has seen this or had any suggestions.

I have recently began playing around with my two servers (Freenas Box and
oVirt box) and their 10Gb Ethernet ports.

I can access the Freenas SMB share over the 10Gb port without issue and I
have been playing around with the capabilities.  After finding out that my
Linux Raid (MDADM) mirror is having horrible write performance, I decided
to plug in an NVMe drive that I had lying around and check out its
performance.

*For my first test*,I added the NVMe drive as a passthrough device to a
Windows guest and was able to transfer to and from Freenas box without
issue.  Speeds were typically ~350-400 MB/s but could drop down to 250 MB/s
or so, and would top out around 525 MB/s, pretty slick!

*For my second test*, I decided to mount the NVMe drive on the CentOS ovirt
host and make it a local datastore.  I migrated my Windows Guest to it, and
decided to test and see what sort of transfer speeds I got and saw some
weird results...

Writing TOO the NAS worked about the same.  Perhaps a little slower but at
least had a steady 250-300 MB/s.

Writing to the Windows Guest had a very "Fast and then slow, fast and then
slow" type of throughput.  I took a few screenshots:

(Writing TO the NAS was fairly consistent)

[image: Inline image 1]
https://i.imgur.com/jWNNvfp.png


(Writing TO the Windows Guest on NVMe storage)
Sometimes these hit the *low 10-20 MB/s* during the transfer.
[image: Inline image 2]
https://i.imgur.com/aizG6n0.png

[image: Inline image 3]
https://i.imgur.com/AjRpR0K.png
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