Re: FreeBSD iscsi target

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

--Nikolay