Re: NetBSD disk performance on VirtualBox

[Sad Clouds <cryintothebluesky%gmail.com@localhost>]

On Sun, 18 Mar 2018 09:44:49 -0500
D'Arcy Cain <darcy%NetBSD.org@localhost> wrote:

> On 03/18/2018 08:41 AM, Sad Clouds wrote:
> > Hello, are there known I/O performance issues with NetBSD on
> > VirtualBox? I've setup two similar VMs, one Linux, another one
> > NetBSD, both use SATA virtual controller with one disk.
> > 
> > Writing 1GB file sequentially:
> > - Linux gives 425MB/sec,
> 
> So about 3400 Mbps.  That's faster SATA I and II and not that much
> less than SATA III and that's just the drive interface.  Actual
> writing to the drive is closer to 150 Mbps.  Maybe more in newer
> drives.
> 
> > - NetBSD gives 27MB/sec.
> 
> That's around 200 Mbps.  That seems closer to the actual drive speed.
> 
> It looks to me like Linux is reporting the write completed as soon as
> it is passed to the kernel while NetBSD waits until it has at least
> been passed to the drive interface.  I hope that system has good
> battery backup.
> 
> -- 
> D'Arcy J.M. Cain <darcy%NetBSD.org@localhost>
> http://www.NetBSD.org/ IM:darcy%Vex.Net@localhost

Not sure what you said is right. The host has LSI MR9260-8i which is
6Gb/sec per port, single SSD disk also supports 6Gb/sec. Surely even on
Linux, if you call fsync() it will block until all data landed on
disk? When I calculate throughput after fsync() returned, I get about
420-450 MBytes/sec on Linux. Why would drive speed be 30-40 MBytes/sec?
That is way too low for modern SSDs.

I think hardware has plenty of bandwidth, there is something about
NetBSD file system or disk driver I/O.