James;
While educating myself in the fine art of Xen I have been
lurking on the list and paying close attention to your incredible drivers.
I spent some time today doing exactly what you asked for, disk performance
testing with and without your PV drivers, so I thought I would share my results
with you and the list along with an interesting observation. I hope you
find this useful and have some ideas on what might be going wrong. Also,
I would like to contribute to Xen in general and this is an area where I feel I
am able to offer some assistance. If there is anything in particular that you
would like me to test in more detail or if you need any more information please
let me know and I will do my best to make the time to work with you on this.
I have a rather large "Windows" estate running on various Hypervisors
so I can probably come up with just about any configuration you want. My current
test configuration is as follows:
Dell Poweredge 1950, Dual 2.0 Ghz 5400 series Intel Procs
, Perc 5i, 2 * SATA 750GB (RAID 1 - WB Cache Enabled in bios and Dom0), 16GB
RAM. All the BIOS' are one version out of date but there are no major
bugs in any of it compelling me to update.
Xen 3.2.1 compiled from source
Dom0 is Centos 5.1
DomU's are on the local storage for testing purposes, an LVM
root partition (default Centos Installation). The only DomU's running on
the machine are the ones mentioned here for these tests and tests were carried
out on one DomU at a time.
All DomU's are fresh installations of: Windows
Server 2003, Standard, R2 SP2 <No windows updates>
I've attached the iometer configuration that I used.
Observation:
I have observed a possible incompatibility between QCOW
image files and the PV drivers. If I create a DomU with the above spec
using an image file created using dd, for example:
dd if=/dev/zero of=guest_disk_sparse.img bs=1k
seek=8192k count=1
Then the drivers work fine.
If I create the image file using:
qemu-img create -f qcow2 giest_disk_qcow.qcow 8G
I get a BSOD.. I can send you a pretty screen shot if you
like. And depending on my "disk" line in the HVM config I get
the BSOD at different times. Tap:aio bsods early in the boot and tap:qcow
bsods quite late.
I double checked these results with two fresh machines,
one running PV 0.9.1 and the other 0.9.5 just to be sure but it would be great
if someone could double check my work?
Obviously I would prefer performance and stability over
the functionality that the QCow disks give me but if this is an easy fix it
would be great to have it all.
IOMETER Performance Results (see config attached)
|
|
Xen
3.2.1
No
Tools
|
Xen
3.2.1
PV
0.95
|
Xen
3.2.1
PV
0.9.1
|
Xen
3.2.1
PV
0.9.5
|
|
Machine Name
|
Qcow1
|
Qcow
|
W2K3
|
RAW
|
|
Image Type
|
QCOW2
|
QCOW2
|
RAW
|
RAW
|
|
MAX IO's
|
|
|
|
|
|
Total I/O's per second
|
1801.43
|
BSOD
|
4385.78
|
16330.33
|
|
Total MBs per Second
|
0.88
|
|
2.14
|
7.97
|
|
Average I/O response Time
|
4.4096
|
|
1.8225
|
0.4890
|
|
MAX Throughput
|
|
|
|
|
|
Total I/O's per second
|
576.76
|
|
1446.27
|
547.64
|
|
Total MBs per Second
|
36.05
|
|
90.39
|
34.23
|
|
Average I/O response Time
|
13.8607
|
|
5.5269
|
14.5923
|
|
RealLife
|
|
|
|
|
|
Total I/O's per second
|
404.61
|
|
6763.00
|
610.42
|
|
Total MBs per Second
|
0.79
|
|
13.21
|
1.19
|
|
Average I/O response Time
|
19.7471
|
|
1.1815
|
13.0836
|
Best Regards
Geoff Wiener
