On Thu, Sep 08, 2011 at 09:25:29PM -0500, Mike Christie wrote: > On 09/08/2011 09:23 PM, Mike Christie wrote: > > On 09/08/2011 04:36 PM, Mike Christie wrote: > >> On 09/08/2011 02:06 AM, Heinrich Langos wrote: > >>> Hi htere, > >>> > >>> I am using the open-iscsi initiator to access a storage back end for > >>> my Xen based virtualization infrastructure. > >>> Since The current 3.0.x Linux kernel finally has everything that I > >>> need to run the host system (Dom0) without any additional patches I > >>> thought I'd give it a try and see if I can replace the 2.6.32 hosts > >>> that cause a lot of trouble when mixing Xen + iSCSI + multipath. > >>> > >>> 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 > >>> > >> > >> I can replicate this now. For some reason I only see it with 1 gig. I > >> think my 10 gig setups that I have been testing with are limited by > >> something else. > >> > >> Doing git bisect now to track down the change that caused the problem. > >>
First of all thank you very much for taking a look at it. I was wondering if I was doing something strange since I havn't seen anybody report anything similar and 2.6.39 is out a while now. But I guess iSCSI users tend to be coporate users and they don't junp on every new kernel version. > > I did not find anything really major in the iscsi code. But I did notice > > that if I just disable iptables throughput goes from about 5 MB/s back > > up to 85 MB/s. > > > > If you disable iptables do you see something similar. > > > > I also noticed that in 2.6.38 throughput would almost immediately start > at 80-90 MB/s, but with 2.6.39 it takes a while (maybe 10 seconds > sometimes) to ramp up. I've noticed the oposite. Throughput starts high and goes down to the numbers reported after about 10 gigabyte. I've noticed with all the kernels I've tested but that is proably a result of the crude way of measuring that I use. I run 'dd if=/dev/disk/by-path/... of=/dev/null bs=1024k &' and 'while kill -USR1 <dd-pid> ; do sleep 2 ; done' . Therefore I usually don't get to see the thoughput during the first couple of seconds. I'm open to suggestions to improve this. I took a look at ip_tables with kernel 3.0.1 (I'll check out the other versions later today.) If I rmmod iptable_filter ip_tables and x_tables the performance starts out higher (over 80 instead of over 60) and drops down to around 63 instead of 43. Still not back up in the region it was before. cheers -henrik -- You received this message because you are subscribed to the Google Groups "open-iscsi" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/open-iscsi?hl=en.
