Is it me or is FreeBSD slower on Xen than Linux?

[rainer at ultra-secure.de]

Am 2016-08-16 16:24, schrieb rainer at ultra-secure.de:
> Am 2016-08-16 16:18, schrieb Roger Pau Monné:
> 
>> I'm not saying it's not possible, but are you sure this slowdown is 
>> caused
>> by the disk? It's certainly a possibility, but I would like to make 
>> sure
>> it's caused by that before jumping into conclusions.
>> 
>> Can you load the full database in RAM and perform the same test. TBH, 
>> I
>> don't use MariaDB, so I'm not sure what's the best way to achieve 
>> this, but
>> a quick search on google shows there are multiple ways. In any case, 
>> make
>> sure with iostat that the database is not read from the disk.
> 
> I'll try to do some disk-benchmarks, when I can attach some bigger 
> disks.

on Ubuntu 14 with HVM:

dc3dd wipe=/dev/xvdc

dc3dd 7.1.614 started at 2016-08-17 09:38:17 +0200
compiled options:
command line: dc3dd wipe=/dev/xvdc
device size: 104857600 sectors (probed)
sector size: 512 bytes (probed)
53687091200 bytes (50 G) copied (100%), 464.642 s, 110 M/s

input results for pattern `00':
    104857600 sectors in

output results for device `/dev/xvdc':
    104857600 sectors out

dc3dd completed at 2016-08-17 09:46:01 +0200


On FreeBSD 10.3-RELEASE-p6 with HVM:

Aug 17 09:57:52 bla-prod kernel: xbd4: 51200MB <Virtual Block Device> at 
device/vbd/51776 on xenbusb_front0
Aug 17 09:57:52 bla-prod kernel: xbd4: features: write_barrier
Aug 17 09:57:52 bla-prod kernel: xbd4: synchronize cache commands 
enabled.

dc3dd wipe=/dev/xbd4

and it's showing 8.something MB/s

Is this normal?
What may I be doing wrong?



Rainer