Problem with FreeBSD as a XenServer Guest - how to debug?

[Rainer Duffner]

> Am 04.02.2017 um 10:48 schrieb Florian Ermisch <florian.ermisch at alumni.tu-berlin.de>:
> 
> Hi Rainer,
> 
> isn't Amazon AWS xen-based?
> I know Colin Percival (cperciva@) is running 
> tarsnap.com on AWS, maybe he knows how 
> to tune it properly?


It’s not a question of tuning.
It’s a factor of 5 that FreeBSD is slower. On SSDs, it’s 10 to 15x.


> Looks like he's the one providing FreeBSD 
> images for AWS, too: https://aws.amazon.com/marketplace/pp/B01LWSWRED/
> Amazon is probably running a heavily patched
> version of Xen but looking at the images' 
> sysctls & stuff and running one on your Xen-
> Server might provide some insights - or at
> least datapoints.
> 
> And then there's DTrace to dive into the 
> kernel's inner workings*…
> 


Yes, but I don’t even know there to start.
My knowledge of Dtrace is very, very limited.




> Oh, does Xen still provide emulation for other
> storage controllers like SATA or SAS? If so
> you may get an at least bearable performance
> using those.


FreeBSD 10 and 11 contain the „optimal“ support for Xen DomU support out-of-the box, AFAIK (the documentation / wiki for Xen is in a horrible state IMO).