Re: [Xen-users] iSCSI performance drop after Linux 2.6.38 ( tested 2.6.39 and 3.0.1 )

[Pasi Kärkkäinen <pasik@xxxxxx>]

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
> 
> 
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