Re: FreeBSD iscsi target

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
> > _______________________________________________
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> 
> 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".