On Thu, Feb 21, 2008 at 11:53:32AM -0800, Sparqz wrote:
> 
> Hi Pasi,
> 
> > > My setup:
> >
> > > 1x HP DL585 - SLES10 x86_64
> > > 1x HP DL585 - RHEL4 x86_64
> > > 1x HP DL380 - SLES10 i586
> >
> > SLES10 or SLES10SP1 ?
> 
> SLES10SP1
> 
> >
> > Have you tried installing and using the latest open-iscsi from 
> > open-iscsi.org ?
> >

OK.. you could try with the latest open-iscsi.org release and see if that
helps.. 


> > > 2x Cisco 2960G (gigabit) switches
> >
> > > 2x Infortrend A16E-G2130-4 with 16x 1TB disks each
> >
> > > The two Infortrend arrays have all their gigabit ethernet ports
> > > plugged into one of the cisco switches, then we have 2 fibre
> > > connections leading to the other cisco switch which has the three
> > > servers plugged into it.  The network is completely isolated from our
> > > other company networks.
> >
> > So you have only 2 gbit/sec of bandwidth between the Cisco switches?
> 
> That's correct.  I've never seen the two links saturated together, the
> most I've seen is ~95% on the first link and ~50% on the second.
> 

OK.

> >
> > How many ethernet ports do your iSCSI arrays have (plugged in to the
> > switches)?
> 
> Each iSCSI array has four 1Gbit ethernet ports, so all four ports are
> connected on each array.
> 

OK.

> >
> > How many ethernet ports each server is using / plugged in to the switch?
> 
> Each server has two 1Gbit ethernet ports - but only one port is used
> on each server for iSCSI traffic, the other is for usual LAN traffic.
> 

OK.

> >
> > > At first I thought it was a network problem, so we replaced our dodgy
> > > Netgear switches with quality Cisco networking gear, but the problem
> > > is the same, if anything it's worse because the Cisco switches
> > > facilitate higher bandwidth (extra ~20mb/s) and the errors seem to be
> > > more reliably producible.
> >
> > Do you see packet drops/errors in any of the ports? Check all ports in both
> > switches.
> 
> No drops and no errors on any of the ports on the servers or on the
> switches.  There's no way to tell what is happening on the iSCSI
> arrays.
> 

So that looks good then..

> >
> > > None of the linux ethernet statistics report any errors (ifconfig) and
> > > the cisco switches don't report any packet errors either.  The
> > > Infortrend arrays don't provide ethernet statistics.
> >
> > Check linux TCP statistics for tcp retransmits? netstat -s
> 
> Tcp:
>     9787 active connections openings
>     4964 passive connection openings
>     8 failed connection attempts
>     885 connection resets received
>     33 connections established
>     1903902036 segments received
>     3106760297 segments send out
>     2108006 segments retransmited
>     0 bad segments received.
>     1298 resets sent
> 
> Looks like there are...  any way to just pull the stats for eth1 ?
> 

So the switches are not dropping packets.. so then the problem has to be in
the arrays? 

> >
> > > Wireshark (ethereal) shows many errors - clusters of Duplicate ACKs,
> > > and a few "previous segment lost".
> >
> > Are you using ethernet flow control? Check the switch settings, and server
> > NIC settings.. and possible iSCSI array settings..
> 
> Someone replied outside of the forum, suggesting I turn on flow
> control.  It's made things a lot faster, but I still see problems with
> packets, and eventually iscsi errors.
> 

OK.

> >
> > In a bigger IP-SAN setup with many servers and switches flow control might 
> > be
> > needed to get a good performance and to prevent tcp retransmits from
> > happening (=preventing the switch port buffers becoming full and packet drop
> > happening).
> >
> > > Any help would be much appreciated !!!
> >
> > Btw have you tried with ext3? XFS is known to have problems with some setups
> > and versions..
> 
> ext3 is worse in my experience.  because our partitions are 1, 2, 5TB
> in size XFS works better for us, especially in the case where the
> partition has to be scanned for errors.  fsck takes hours on large
> multiple terabyte arrays!  xfs_check takes only a few minutes.
> Although, it could just be the amount of IO that fsck.ext3 does that
> causes iscsi problems and delays etc.
> 
> >
> > I'm not familiar with Infotrend iSCSI arrays so can't comment much about
> > them..
> 
> I get that a lot )-;
> 

Are those Infotrend arrays certified/supported with open-iscsi? or SLES10? 

-- Pasi

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