Henrik Langos
2011-Sep-07 16:20 UTC
[Xen-users] iSCSI performance drop after Linux 2.6.38 ( tested 2.6.39 and 3.0.1 )
I know it is not directly Xen related but since the 3.0 Linux kernel finally contains pretty much everything that you need to run your Dom0, I thought that I might share my observations with anybody who''s using iSCSI as storage backend for their Xen installation. This is raw "dd" throughput for reading ~30GB from an iSCSI storage via a dedicated 1GB Ethernet link. 2.6.32 : 102 MB/s 2.6.38 : 100 MB/s 2.6.39 : 44 MB/s 3.0.1 : 43 MB/s Seems like between 2.6.38 and 2.6.39 the iSCSI performance got pretty much thrown out the window ... If I were into into conspiracy theories I''d suspect that the Core-iSCSI guys are out to prove the superior performance of their initiator by slowing down the open-iSCSI competitor. ;-) (See http://linux-iscsi.org/wiki/Core-iSCSI#Performance ) I tested with Debian Squeeze on bare metal to remove Xen from the equation and I tested without multipath to avoid those complications too. Kernel 2.6.32 is the default Squeeze kernel, 2.6.38 and 2.6.39 were from squeeze-backports and 3.0.1 was built from the vanilla kernel sources using make-kpkg. The storage is a Dell / Equallogic PS4000. Please drop me a line if you can confirm or refute those findings. On the positive side I have to say that the 3.0.1 kernel is much more stable in my Xen + iSCSI + multipath setup. (Though I havn''t yet tested it with the load that I have on the 2.6.32 machine.) Cheers -henrik _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Pasi Kärkkäinen
2011-Sep-07 18:22 UTC
Re: [Xen-users] iSCSI performance drop after Linux 2.6.38 ( tested 2.6.39 and 3.0.1 )
On Wed, Sep 07, 2011 at 06:20:13PM +0200, Henrik Langos wrote:> I know it is not directly Xen related but since the 3.0 Linux kernel > finally contains pretty much everything that you need to run your Dom0, > I thought that I might share my observations with anybody who''s using > iSCSI as storage backend for their Xen installation. > > This is raw "dd" throughput for reading ~30GB from an iSCSI storage via > a dedicated 1GB Ethernet link. > > 2.6.32 : 102 MB/s > 2.6.38 : 100 MB/s > 2.6.39 : 44 MB/s > 3.0.1 : 43 MB/s > > Seems like between 2.6.38 and 2.6.39 the iSCSI performance got pretty > much thrown out the window ... >Hello, You should write to open-iscsi mailinglist.. -- Pasi> If I were into into conspiracy theories I''d suspect that the Core-iSCSI > guys are out to prove the superior performance of their initiator by > slowing down the open-iSCSI competitor. ;-) > (See http://linux-iscsi.org/wiki/Core-iSCSI#Performance ) > > > I tested with Debian Squeeze on bare metal to remove Xen from the > equation and I tested without multipath to avoid those complications too. > Kernel 2.6.32 is the default Squeeze kernel, 2.6.38 and 2.6.39 were > from squeeze-backports and 3.0.1 was built from the vanilla kernel > sources using make-kpkg. The storage is a Dell / Equallogic PS4000. > > Please drop me a line if you can confirm or refute those findings. > > On the positive side I have to say that the 3.0.1 kernel is much more > stable in my Xen + iSCSI + multipath setup. (Though I havn''t yet tested > it with the load that I have on the 2.6.32 machine.) > > Cheers > -henrik > > > _______________________________________________ > 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