Re: FreeBSD iscsi target

On Thu, Jul 3, 2014 at 2:13 AM, Slawa Olhovchenkov <slw_at_zxy.spb.ru> wrote:

> On Thu, Jul 03, 2014 at 09:31:45AM +0100, Nikolay Denev wrote:
>
> > On Thu, Jul 3, 2014 at 12:06 AM, Kevin Oberman <rkoberman_at_gmail.com>
> wrote:
> > > On Wed, Jul 2, 2014 at 1:36 PM, Slawa Olhovchenkov <slw_at_zxy.spb.ru>
> wrote:
> > >
> > >> On Wed, Jul 02, 2014 at 12:51:59PM -0700, Kevin Oberman wrote:
> > >>
> > >> > On Wed, Jul 2, 2014 at 4:26 AM, Slawa Olhovchenkov <slw_at_zxy.spb.ru>
> > >> wrote:
> > >> >
> > >> > > On Tue, Jul 01, 2014 at 10:43:08PM -0700, Kevin Oberman wrote:
> > >> > >
> > >> > > > On Tue, Jul 1, 2014 at 4:13 PM, Slawa Olhovchenkov <
> slw_at_zxy.spb.ru>
> > >> > > wrote:
> > >> > > >
> > >> > > > > On Tue, Jul 01, 2014 at 11:12:52AM +0200, Edward Tomasz
> Napierala
> > >> > > wrote:
> > >> > > > >
> > >> > > > > > Hi.  I've replied in private, but just for the record:
> > >> > > > > >
> > >> > > > > > On 0627T0927, Sreenivasa Honnur wrote:
> > >> > > > > > > Does freebsd iscsi target supports:
> > >> > > > > > > 1. ACL (access control lists)
> > >> > > > > >
> > >> > > > > > In 10-STABLE there is a way to control access based on
> initiator
> > >> > > > > > name and IP address.
> > >> > > > > >
> > >> > > > > > > 2. iSNS
> > >> > > > > >
> > >> > > > > > No; it's one of the iSCSI features that seem to only be used
> > >> > > > > > for marketing purposes :-)
> > >> > > > > >
> > >> > > > > > > 3. Multiple connections per session
> > >> > > > > >
> > >> > > > > > No; see above.
> > >> > > > >
> > >> > > > > I think this is help for 40G links.
> > >> > > > >
> > >> > > >
> > >> > > > I assume that you are looking at transfer of large amounts of
> data
> > >> over
> > >> > > 40G
> > >> > > > links. Assuming that tis is the case, yes, multiple connections
> per
> > >> > > session
> > >> > >
> > >> > > Yes, this case. As I know, single transfer over 40G link limited
> by
> > >> > > 10G.
> > >> > >
> > >> > ??? No, not at all. Getting 40G performance over TCP is not easy,
> but
> > >> there
> > >> > is no 10G limitation.
> > >>
> > >> As I know (may be wrong) 40G is bundled 4x10G link.
> > >> For prevent packet reordering (when run over diferrent link) all
> > >> packets from one sessoin must be routed to same link.
> > >> Same issuse for Etherchannel.
> > >>
> > >
> > > No, 40G Ethernet is  single channel from the interface perspective..
> What
> > > my be confusing you is that they may use "lanes" which, for 40G,  are
> > > 10.3125G. But, unlike the case with Etherchannel, these lanes are
> "hidden"
> > > from the MAC. The interface deals with a single stream and parcels it
> out
> > > over the 10G (or 25G) lanes. All 100G optical links use multiple lanes
> > > (4x25G or 10x10G), but 40G my use either a single 40G lane for
> distances of
> > > up to 2km or 4x10G for longer runs.
> > >
> > > Since, in most cases, 40G is used within a data center or to connect to
> > > wave gear for DWDM transmission over very long distances, most runs are
> > > under 2km, so a single 40G lane may be used. When 4 lanes are used, a
> > > ribbon cable is required to assure that all optical or copper paths are
> > > exactly the same length. Since the PMD is designed to know about and
> use
> > > these lanes for a single channel, the issue of packet re-ordering is
> not
> > > present and the protocol layers above the physical are unaware of how
> many
> > > lanes are used.
> > >
> > > Wikipedia has a fairly good discussion under the unfortunate title of
> 100
> > > Gigabit Ethernet <https://en.wikipedia.org/wiki/100_Gigabit_Ethernet>.
> > > Regardless of the title, the article covers both 40 and 100 Gigabit
> > > specifications as both were specified on the same standard, 802.3ba.
> > >
> > > --
> > > R. Kevin Oberman, Network Engineer, Retired
> > > E-mail: rkoberman_at_gmail.com
> > > _______________________________________________
> > > freebsd-current_at_freebsd.org mailing list
> > > http://lists.freebsd.org/mailman/listinfo/freebsd-current
> > > To unsubscribe, send any mail to "
> freebsd-current-unsubscribe_at_freebsd.org"
> >
> > I found this white paper useful in understanding how this works :
> >
> http://www.cisco.com/c/en/us/products/collateral/switches/nexus-3000-series-switches/white_paper_c11-726674.pdf
>
> In real world "Reality is quite different than it actually is".
>
> http://www.cisco.com/c/en/us/products/collateral/switches/catalyst-6500-series-switches/white_paper_c11-696669.html
>
> See "Packet Path Theory of Operation. Ingress Mode".
>
>
Yep. It is really crappy LAGG (fixed three-tupple hash... yuck!) and is
really nothing but 4 10G Ethernet ports using a 40G PHY in yhe 4x10G form.

Note that they don't make any claim of 802.3ba compliance. It only states
that "40 Gigabit Ethernet is now part of the IEEE 802.3ba standard." So it
is, but this device almost certainly predates the completion of the
standard to get a product for which there was great demand. It's a data
center product and for typical cases of large numbers of small flow, it
should do the trick. Probably does not interoperate with true 80-2.3ba
hardware, either.

My boss at the time I retired last November was on the committee that wrote
802.3ba. He would be a good authority on whether the standard has any vague
wording that would allow this, but he retired 5 month after I did and I
have no contact information for him. But I'm pretty sure that there is no
way that this is legitimate 40G Ethernet.
-- 
R. Kevin Oberman, Network Engineer, Retired
E-mail: rkoberman_at_gmail.com