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

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

On Tue, Feb 02, 2021 at 03:55:10PM +0100, BERTRAND Joël wrote:
> Michael van Elst a écrit :
> > joel.bertrand%systella.fr@localhost (=?UTF-8?Q?BERTRAND_Jo=c3=abl?=) writes:
> > 
> >> 	But jumbo frames and Intel adapter don't increase NAS throughput :
> >>              204Mb           407Mb           611Mb           814Mb
> > 
> > Where does this information come from?
> 
> 	iftop.

But with what kind of disk operation?

iSCSI naturally has a higher latency than a direct attached disk.
To utilize a link you may need to generate more requests in parallel.

For writing that's not that difficult as the client will buffer enough
data. For reading you need large buffers or significant read-ahead to
trigger concurrent I/O.

You may also need to tune TCP/IP on the client.

You could start a test with reading from the raw iSCSI volume
with dd. You need a read buffer of at least 1MB to get the
maximal concurrency.

> [ ID] Interval           Transfer     Bitrate
> [  5]   0.00-10.00  sec  1.08 GBytes   931 Mbits/sec

That looks reasonable for a Gigabit interface.


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