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

[bugzilla-noreply]

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

--- Comment #6 from k...@pielorz.com ---
(In reply to rainer from comment #5)

Ok, so 'like for like' test see's better performance.

I'm not overly familiar with dc3dd - maybe it's using a "really small block
size" - and  on your setup, this is causing an issue (maybe look at the ssz /
bufsz options)

Do you have any 'local storage' on XenServer (or can you create some) - i.e.
something you can map to a FreeBSD VM - and repeat both the dc3dd and dd test
on - that is backed by a local SATA / SAS disk on XenServer (i.e. not going
through ScaleIO?)

-Karl

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

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

--- Comment #5 from rai...@ultra-secure.de ---
10.3-RELEASE-p5:

(server ) 0 # time dd if=/dev/zero of=test.dat bs=64k count=20480
20480+0 records in
20480+0 records out
1342177280 bytes transferred in 1.769942 secs (758317078 bytes/sec)
dd if=/dev/zero of=test.dat bs=64k count=20480  0.02s user 1.75s system 99% cpu
1.775 total
(server ) 0 # time dd if=/dev/zero of=test.dat bs=64k count=204800
204800+0 records in
204800+0 records out
13421772800 bytes transferred in 17.266468 secs (777331701 bytes/sec)
dd if=/dev/zero of=test.dat bs=64k count=204800  0.15s user 17.06s system 99%
cpu 17.271 total

This is ZFS.
Probably due to compression on.


root@other-server:/srv# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:Ubuntu 14.04.4 LTS
Release:14.04
Codename:   trusty
root@other-server:/srv# time dd if=/dev/zero of=test.dat bs=64k count=20480
20480+0 records in
20480+0 records out
1342177280 bytes (1.3 GB) copied, 2.5559 s, 525 MB/s

real0m2.571s
user0m0.041s
sys 0m2.125s

root@other-server:/srv# time dd if=/dev/zero of=test.dat bs=64k count=204800
204800+0 records in
204800+0 records out
13421772800 bytes (13 GB) copied, 93.6892 s, 143 MB/s

real1m33.940s
user0m0.219s
sys 0m26.136s


root@yet-another-server:/srv# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:Ubuntu 16.04.1 LTS
Release:16.04
Codename:   xenial
root@yet-another-server:/srv# time dd if=/dev/zero of=test.dat bs=64k
count=20480
20480+0 records in
20480+0 records out
1342177280 bytes (1.3 GB, 1.2 GiB) copied, 1.62124 s, 828 MB/s

real0m1.652s
user0m0.004s
sys 0m1.616s
root@yet-another-server:/srv# time dd if=/dev/zero of=test.dat bs=64k
count=204800
204800+0 records in
204800+0 records out
13421772800 bytes (13 GB, 12 GiB) copied, 100.348 s, 134 MB/s

real1m40.711s
user0m0.172s
sys 0m25.004s


So, in this particular test, it's actually faster.
But I can assure you, in practical use, it's not.


10.3-RELEASE-p7, UFS:

(freebsd-srv2 ) 0 # time dd if=/dev/zero of=test.dat bs=64k count=20480
20480+0 records in
20480+0 records out
1342177280 bytes transferred in 8.746548 secs (153452229 bytes/sec)
dd if=/dev/zero of=test.dat bs=64k count=20480  0.02s user 1.65s system 19% cpu
8.756 total
(freebsd-srv2 ) 0 # time dd if=/dev/zero of=test.dat bs=64k count=204800
204800+0 records in
204800+0 records out
13421772800 bytes transferred in 99.078364 secs (135466233 bytes/sec)
dd if=/dev/zero of=test.dat bs=64k count=204800  0.22s user 18.20s system 18%
cpu 1:39.30 total

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

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

--- Comment #3 from rai...@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 ) 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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[Bug 212681] I/O is slow for FreeBSD DOMu on XenServer

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

Daniel Ylitalo  changed:

   What|Removed |Added

 CC||dan...@blodan.se

--- Comment #2 from Daniel Ylitalo  ---
We use XenServer 7 overhere and we can't run FreeBSD vm's on it unfortunately.
(Tried both 11-RC1 and 10.3) (We use local storage)

Just a regular "portsnap fetch extract" takes like 10 times the time it does on
a baremetal server.

So when someone requests a FreeBSD server they get a baremetal one, all
variants of linux gets a vm.

I'm happy to provide a vm if someone is eager to troubleshoot this, I've tried
all solutions out there in the xen I/O mail threads/forum posts but none did
the trick.

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

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

k...@pielorz.com changed:

   What|Removed |Added

 CC||k...@pielorz.com

--- Comment #1 from k...@pielorz.com ---
Hi,

We run XenServer 6.5 and 7 here - with a range of FreeBSD versions (mostly 10.x
now). We've not noticed any really low I/O performance.

How are you running dc3dd? - So I can try and install / replicate this here.

We have seen that I/O behaves differently under XenServer than it does on bare
metal (which is obvious - i.e. local SATA SSD vs. Multipath iSCSI [or similar])
you will see differences (even just with 'mapped through XenServer' "Local
Storage").

It could be dc3dd / the stuff you're running is a particularly 'bad case' for
the I/O. e.g. In an equally 'synthetic' test - a regular "dd if=/dev/zero
of=test.dat bs=64k count=10240" on our our test pool here (which has two paths
iSCSI over Gigabit) we get around 220Mbyte/sec to a FreeBSD DomU.

That may well be a best case - and you may well have hit some worst cases.

-Karl

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