On 09/04/2009 06:54 AM, Angel L. Mateo wrote:
> Hello everyone,
>       I am introducing myself to iSCSI world, so maybe these are newbie
> questions. I'm sorry.
>       My first test has been to create a LUN (in a celerra file server) and
> export it with iscsi. I have mounted this lun in a debian server
> (lenny), created a file system, and mounted it. The problem I have is
> that performance is poor than in a NFS FS (with NFS I get ~50MB/s and
> with iSCSI I get ~10MB/s). I am mounting NFS and iSCSI filesystem over a
> bonding (active/pasive) of two gigabit cards. I am using tcp transport
> for iSCSI.

Can you try different IO schedulers

echo noop > /sys/block/sdXYZ/queue/scheduler

And for your IO test what are you using and what IO sizes are used? For 
a good throughput you want lots of IO (around the queue depth of the 
target which is probably around 128 or 256) and larger IOs (around 64 or 

>       Another question related with this, is that one of my cards is a
> Broadcom NetXtremm II BMC5708S wich supports iSCSI. Although some man
> pages talk about a bnx2i transport, I haven't found any kernel module
> for this. Could I use this transport? How? Should it improves
> performance?

You cannot use this transport with the upstream open-iscsi tools. The 
2.6.31 kernel will have a bnx2i driver for that card, but you will still 
need a special broadcom daemon to use the offload capabilites of the 
card. Broadcom and other offload guys like Chelsio are working on 
merging a common daemon/lib into the open-iscsi package right now.

I will let the broadcom guys talk about perf more because I do not have 
any numbers handy. From my testing I have seen it performs well with 
smaller IOs (less than 32K) and iscsi_tcp does not. With larger IOs and 
lots of them the throughput seems to the be same (at least with a 1 gig 
network), but the braodcom cpu usage is much less. iscsi_tcp has a xmit 
thread which can take up almost 100% of the cpu at times, but broadcom 
does not have that thread since it does the same operations in hardware.

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