Re: Network very very slow... was iSCSI and jumbo frames

[RVP <rvp%SDF.ORG@localhost>]

On Mon, 8 Feb 2021, BERTRAND Joël wrote:

> 	I haven't spare disks enough. Thus, I have created a disk image on a
> Linux laptop (with an old AMD E-450), installed istgt and exported this
> disk.
>
> legendre# dd if=/dev/rsd1a of=/dev/null iflag=direct bs=1m count=10000
> 10000+0 records in
> 10000+0 records out
> 10485760000 bytes transferred in 156.383 secs (67051789 bytes/sec)
>
> 	Throughput is more or less 500 Mbps on network, but there are some
> limiting factors :
> - CPU (but istgt only takes 60% of one thread) ;
> - hard disk ;
> - Ethernet adapter (Qualcomm Atheros)...
>
> 	But 67 MBps is greater than 10 MBps I obtain with NAS.

This, and the other tests show that NetBSD iscsi initiator is OK.

> 	I have captured tcpdump output on both adapters (I post only one second) :
> ...
> 	Often, network stops during 90 or 100 ms (see the last lines). On agr0
> (to riemann), I don't see these 'stops'.

Since we are only interested in the timing and the headers, create
tcpdump with a small snaplen like this:

tcpdump -i wm0 -s 128 -w 1.dump

A snaplen of 128 is sufficient for our purposes and, compressed
with xz(1), the entire dump of a 10GB iscsi xfer takes only ~15 MB
with no lost packets.

> 	On euclide, there is no istgt, but a iscsid (iscsid version 2.0-871)
> and I don't understand how this daemon is started as
> /etc/config/iscsi/sbin/iscsid.conf doesn't exists !
> ...
> [/] # cd /etc/config/iscsi
> -sh: cd: /etc/config/iscsi: No such file or directory
> [/] # ls /etc/config/iscsi/sbin/iscsid.conf
> ls: /etc/config/iscsi/sbin/iscsid.conf: No such file or directory
> [/] #

Try: find / -name *.conf OR find / -iname *scsi*
on euclide. It is possible that the throttling is being done on
the NAS for non-Linux initiators (though why it would be, I don't
know).

Also (on euclide):
1. Try to locate the iscsi target config file and see what ACLs
   are in there.

2. Find out if any network Traffic Control is being done.

3. Look through these log-file:

   /var/log/network/err_log
   /var/log/network/events_log

4. Try to find out what these commands or scripts do:

   /sbin/gen_bandwidth
   /usr/local/bin/rates_monitor_start

> 	OK, iscsid is started without config file (I don't understand why it
> doesn't stop immediatly), but it runs fine with Linux initiator...

I didn't understand this bit. If one instance of iscsid is running
at port 3260, how did you manage to run another one--it should've
complained that the port was already in use.

-RVP