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

[Michael van Elst <mlelstv%serpens.de@localhost>]

On Mon, Feb 08, 2021 at 10:13:16AM +0100, BERTRAND Joël wrote:

> 	I don't undestand how dd returns "no such file or directory" when I try :
> 
> legendre# dd if=/dev/zero of=/opt/test iflag=direct oflag=direct
> count=5000 bs=1m
> dd: /opt/test: No such file or directory

oflag is the list of all open flags. If the output file doesn't exist,
then open needs the O_CREAT flag to create it. The default open flags
also include O_TRUNC to erase the previous file contents.

So you can use:    oflag=creat,trunc,direct


The in-kernel initiator logs debug info when you set hw.iscsi.debug
to a debug level > 0.

1 -> basic start/stop events, ioctls
5 -> more events, log commands and queue status
9 -> add handshake events
10 -> trace communication, task management, scsipi calls
11 -> iSCSI windowing
15 -> trace CCB/PDUs
99 -> log uio, network, scsipi_done

Level 9 is already pretty verbose.


For the "dd"-test of iSCSI, use the raw devices (not block devices,
not files in a filesystem) and a block size of 1MB. Only if that
works ok, it makes sense to look at filesystem I/O, i.e. your /opt
filesystem.


Greetings,
-- 
                                Michael van Elst
Internet: mlelstv%serpens.de@localhost
                                "A potential Snark may lurk in every tree."