[pve-devel] openiscsi vs libiscsi

[Alexandre DERUMIER]

I have done some tests 


with opensscsi vs libiscsi 


on a gigabit link 


open-iscsi: 15000iops 
libiscsi: 21000iops (gigabit limited) 


So yes, something must be wrong with current openscsi. 


don't know if it's related, but in 2.6.38 
http://kerneltrap.org/mailarchive/linux-scsi/2010/12/31/6888002 
" They fix a couple bugs and remove the host lock from the queuecommand path." 

----- Mail original -----

De: "Alexandre DERUMIER" <aderumier at odiso.com> 
À: "Stefan Priebe - Profihost AG" <s.priebe at profihost.ag> 
Cc: pve-devel at pve.proxmox.com 
Envoyé: Lundi 23 Juillet 2012 11:57:37 
Objet: Re: [pve-devel] little iops with PVE kernel than vanilla 3.5 

Maybe can you try to backport scsi module from 3.5 kernel ? 

BTW,I never test the multi-sessions,seem to be very new in 2.0.873. 
How do you configure multi-session ? 


from open-icsi doc, for module compilation: 


"By default the kernel's iSCSI modules will be used. Running: 

make 
make install 

will install the iSCSI tools iscsiadm and iscsid to /sbin. 

For 2.6.14 - 2.6.34 the modules in the kernel dir can built and install 
by running: 

make kernel 

When building those modules the kernel source found at 
/lib/modules/`uname -a`/build 
will be used to compile the open-iscsi modules. To specify a different 
kernel to build against use: 

make kernel KSRC=<kernel-src> 

or cross-compilation: 

make kernel KSRC=<kernel-src> KARCH="ARCH=um" 

To compile on SUSE Linux you'll have to use 

make kernel KSRC=/usr/src/linux \ 
KBUILD_OUTPUT=/usr/src/linux-obj/<arch>/<config> 

where <config> is the kernel configuration to use (eg. 'smp'). 

To install the kernel modules that were built run: 

make install_kernel 

This will copy: iscsi_tcp.ko, libiscsi_tcp.ko, libiscsi.ko and 
scsi_transport_iscsi to 
/lib/modules/`uname -r`/kernel/drivers/scsi/ 
overwriting existing iscsi modules. 

For Debian, be sure to install the linux-headers package that 
corresponds to your kernel in order to compile the kernel modules 
('aptitude install linux-headers-`uname -r`'). You may also wish to 
run 'make -C kernel/ dpkg_divert' before installing kernel modules if 
you run a Debian-provided kernel. This will use dpkg-divert(8) to 
move the packaged kernel modules out of the way, and ensure that 
future kernel upgrades will not overwrite them. 

Also, please be aware that the compatibility patches that enable these 
iscsi modules to run on kernels older than 2.6.25 will not update the 
ib_iser module; you may get warnings related to mismatched symbols on 
this driver, in which case you'll be unable to load ib_iser and 
open-iscsi simultaneously. 
" 

----- Mail original ----- 

De: "Stefan Priebe - Profihost AG" <s.priebe at profihost.ag> 
À: "Alexandre DERUMIER" <aderumier at odiso.com> 
Cc: pve-devel at pve.proxmox.com, "Martin Maurer" <martin at proxmox.com> 
Envoyé: Lundi 23 Juillet 2012 09:32:57 
Objet: Re: [pve-devel] little iops with PVE kernel than vanilla 3.5 

Am 22.07.2012 19:24, schrieb Alexandre DERUMIER: 
> Maybe the iscsi module is faster on 3.5 ? 
> But It could be also network driver, or something else in the kernel. 
No both tested. Both has the same speed. 

See my posted part here: 
> On my KVM Host i get constant 100.000 4k random iops with vanilla 3.5 
> and latest PVE kernel - so no difference. 

> Did you have tested fio directly on the host ? (with the 2 differents kernel). 
> I would like to see if the slowdown come from kvm or not. 
Yes host speed is the same. 

Stefan 



-- 

-- 





Alexandre D e rumier 

Ingénieur Systèmes et Réseaux 


Fixe : 03 20 68 88 85 

Fax : 03 20 68 90 88 


45 Bvd du Général Leclerc 59100 Roubaix 
12 rue Marivaux 75002 Paris 

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-- 



	
Alexandre D e rumier 
Ingénieur Systèmes et Réseaux 

Fixe : 03 20 68 88 85 

Fax : 03 20 68 90 88 

45 Bvd du Général Leclerc 59100 Roubaix 
12 rue Marivaux 75002 Paris 

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