[Bug 212681] I/O is slow for FreeBSD DOMu on XenServer

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=212681

--- Comment #3 from rainer at ultra-secure.de ---
Our hardware is local disks (not SSDs) networked via ScaleIO.

I've run a dd from one disk of a VM to another one and it was very, very slow.

OS: "Other (64bit)" (which is actually a little bit faster than choosing
"FreeBSD 10"

(freebsd11 </root>) 0 # dc3dd wipe=/dev/ada1

dc3dd 7.2.641 started at 2016-08-18 13:24:02 +0200
compiled options:
command line: dc3dd wipe=/dev/ada1
device size: 104857600 sectors (probed), 53,687,091,200 bytes
sector size: 512 bytes (probed)
53687091200 bytes ( 50 G ) copied ( 100% ), 3084 s, 17 M/s

input results for pattern `00':
104857600 sectors in

output results for device `/dev/ada1':
104857600 sectors out

dc3dd completed at 2016-08-18 14:15:26 +0200


The question remains: why is this and what can one do?

One of our customers has an application-workload (php+mysql) that takes 3s to
process on an Ubuntu 16 VM with 2 vCPUs and 8GB RAM.
The FreeBSD VM is completely unusable for this because it's bogged down to a
halt, regardless of how many vCPUs and RAM I give it.

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