On Sun, 18 Mar 2018 09:44:49 -0500 D'Arcy Cain <da...@netbsd.org> 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 <da...@netbsd.org> > http://www.NetBSD.org/ IM:da...@vex.net 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.
