Hi All,
We''re seeing some really poor disk performance under Xen Source. Below
are the output of some Bonnie++ tests ran on the underlying host as well as on a
HVM instance. We''ve seen the same level of performance on Debian Etch
and Debian Lenny. Can anyone comment on what we might do to improve this and get
near-native performance from a HVM machine.
Host - Running Centos 5.3
Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
tig-xen-host-1. 14G 212037 38 115111 19 300545 12 779.4
Write: 207MB/s
Rewrite: 112MB/s
Read: 293.5MB/s
Guest host - running Centos 5.3
Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
localhost.locald 2G 29566 4 21399 5 88812 9 497.7 6
localhost.localdomain,2G,,,29566,4,21399,5,,,88812,9,497.7,6,,,,,,,,,,,,,
Write speed: 28.87MB/s
Rewrite speed: 20.89MB/s
Read: 86.73MB/s
Thanks
Gavin
Gavin Conway
Senior Engineer, Operations (Systems Group), UKSolutions
Telephone: 0845 004 1333, option 2
Email: gavin.conway@uksolutions.co.uk
Web: http://www.uksolutions.co.uk/
UKS Ltd, Birmingham Road, Studley, Warwickshire, B80 7BG Registered in England
Number 3036806
This email must be read in conjunction with the legal & service notices on
http://www.uksolutions.co.uk/disclaimer
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On Fri, Jul 31, 2009 at 11:32:53AM +0100, Gavin Conway wrote:> Hi All, > > We''re seeing some really poor disk performance under Xen Source. > Below are the output of some Bonnie++ tests ran on the underlying host > as well as on a HVM instance. We''ve seen the same level of performance > on Debian Etch and Debian Lenny. Can anyone comment on what we might do > to improve this and get near-native performance from a HVM machine. >Why do you need HVM guest? HVM, aka fully virtualized guests use Qemu to _emulate_ IDE (or SCSI) adapters and disks, so that''ll be slow. If you can''t switch to paravirtual (PV) guests, at least try to install PV-on-HVM drivers, which should help a lot. Other possibility is to use stubdoms with HVM, but that''s not available in Xen shipped in CentOS 5.3. Stubdoms can be found from Xen 3.4.x PV guests will be a lot faster, since there''s no need for emulation. I recommend you to run PV guests. -- Pasi> > > Host - Running Centos 5.3 > > Version 1.03 ------Sequential Output------ --Sequential Input- --Random- > -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- > Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP > tig-xen-host-1. 14G 212037 38 115111 19 300545 12 779.4 > > Write: 207MB/s > Rewrite: 112MB/s > Read: 293.5MB/s > > > Guest host - running Centos 5.3 > > Version 1.03 ------Sequential Output------ --Sequential Input- --Random- > -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- > Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP > localhost.locald 2G 29566 4 21399 5 88812 9 497.7 6 > localhost.localdomain,2G,,,29566,4,21399,5,,,88812,9,497.7,6,,,,,,,,,,,,, > > Write speed: 28.87MB/s > Rewrite speed: 20.89MB/s > Read: 86.73MB/s > > > Thanks > Gavin > > > Gavin Conway > Senior Engineer, Operations (Systems Group), UKSolutions > > Telephone: 0845 004 1333, option 2 > Email: gavin.conway@uksolutions.co.uk > Web: http://www.uksolutions.co.uk/ > UKS Ltd, Birmingham Road, Studley, Warwickshire, B80 7BG Registered in England Number 3036806 > This email must be read in conjunction with the legal & service notices on http://www.uksolutions.co.uk/disclaimer > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> Why do you need HVM guest? HVM, aka fully virtualized guests use Qemu > to _emulate_ IDE (or SCSI) adapters and disks, so that''ll be slow. > > If you can''t switch to paravirtual (PV) guests, at least try to > install > PV-on-HVM drivers, which should help a lot. Other possibility is to > use > stubdoms with HVM, but that''s not available in Xen shipped in CentOS > 5.3. > Stubdoms can be found from Xen 3.4.x > > PV guests will be a lot faster, since there''s no need for emulation. > I recommend you to run PV guests.Hi Pasi, We get the same performance under windows but comparing the difference between the two it''s easier to demonstrate with 2 x Linux systems. With regards to why we use HVM, this is so we can do P2V migrations of various OS'' into Xen. Could you link me to the PV-on-HVM drivers for Linux, these sound like a good way forward. Also Stubdoms are a new one on me, do you know of any recommended reading. Googling draws up a blank apart from problems people have had. Thanks Gavin Gavin Conway Senior Engineer, Operations (Systems Group), UKSolutions Telephone: 0845 004 1333, option 2 Email: gavin.conway@uksolutions.co.uk Web: http://www.uksolutions.co.uk/ UKS Ltd, Birmingham Road, Studley, Warwickshire, B80 7BG Registered in England Number 3036806 This email must be read in conjunction with the legal & service notices on http://www.uksolutions.co.uk/disclaimer _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Fri, Jul 31, 2009 at 11:59:50AM +0100, Gavin Conway wrote:> > Why do you need HVM guest? HVM, aka fully virtualized guests use Qemu > > to _emulate_ IDE (or SCSI) adapters and disks, so that''ll be slow. > > > > If you can''t switch to paravirtual (PV) guests, at least try to > > install > > PV-on-HVM drivers, which should help a lot. Other possibility is to > > use > > stubdoms with HVM, but that''s not available in Xen shipped in CentOS > > 5.3. > > Stubdoms can be found from Xen 3.4.x > > > > PV guests will be a lot faster, since there''s no need for emulation. > > I recommend you to run PV guests. > > Hi Pasi, > > We get the same performance under windows but comparing the difference between > the two it''s easier to demonstrate with 2 x Linux systems. With regards to why we use HVM, > this is so we can do P2V migrations of various OS'' into Xen. >For windows you should use PV-on-HVM drivers aswell, check the GPLPV drivers. That way you''ll get a LOT better performance. You can do Linux P2V to PV guest aswell, no need to run HVM.> Could you link me to the PV-on-HVM drivers for Linux, these sound like a good way forward. > Also Stubdoms are a new one on me, do you know of any recommended reading. Googling draws up a blank apart from problems people have had. >http://blog.xen.org/index.php/2008/08/28/xen-33-feature-hvm-device-model-domain/ http://www.xen.org/files/xensummitboston08/SamThibault_XenSummit.pdf Check those out. -- Pasi _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> -----Original Message----- > We get the same performance under windows but comparing the difference between > the two it''s easier to demonstrate with 2 x Linux systems. With regards to why we use > HVM, this is so we can do P2V migrations of various OS'' into Xen.For Linux, a HVM to PV migration shouldn''t be a barrier. Install a pv-ops capable kernel in your domU (or 2.6.18 Xen-patched kernel), adjust configs and restart the domU. You can also stick with HVM, but why cripple things? Wouldn''t you rather have device hotplug, balloon and fast I/O? For Windows you can install the GPLPV driver to avoid emulated I/O. I don''t know what options exist for any other OS. Jeff _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users