Why VMware Virtual disk so slow (da0: 3.300MB/s transfers) ?

[Justin Sherrill]

On Wed, Aug 21, 2013 at 12:01 PM, Dongsheng Song
<dongsheng.song at gmail.com> wrote:

>> 1073741824 bytes (1.1 GB) copied, 2.10386 s, 510 MB/s
>> 1073741824 bytes (1.1 GB) copied, 7.08881 s, 151 MB/s
>> 1073741824 bytes (1.1 GB) copied, 6.85367 s, 157 MB/s

> 1073741824 bytes transferred in 34.246246 secs (31353563 bytes/sec)
> 1073741824 bytes transferred in 17.962520 secs (59776793 bytes/sec)
> 1073741824 bytes transferred in 50.373031 secs (21315807 bytes/sec)

In other operating systems, you are seeing 3-4x variations in speed in
the exact same test.  Something not in that virtual installation is
eating up disk time; it is hard to reach any conclusion when you are
seeing such variation in your 'control' tests.

It's possible that DragonFly doesn't perform as well for disk I/O in
emulation, and I know there's been virtio driver work that could
benefit that.  But - there's something else going on.