Thanks for your reply Nicholas. Just a few questions
:D
--- "Nicholas A. Bellinger" <nickb@xxxxxxxx> wrote:
> Greetings All!
>
> Registered iSCSI logical units provided to the host
> OSes SCSI subsystem
> speaking ERL=2 can preform session continuation
> within the context of
> its own iSCSI Nexus.
So it's mainly useful for session continuation (which
is a nice feature). But does it affect data integrity
in any way? Would using plain erl=0 with HeaderDigest
and BodyDigest give you everything that erl=2 gives
you without session continuation, or could erl=2
prevent certain data corruption that erl=0 combined
with HeaderDigest and BodyDigest can't protect you
from?
> Traditional outernexus
> multipath software
> (dm-multipath, MPIO, and others) require multiple
> iSCSI sessions to be
> created to different ISIDs to same or different
> iSCSI TPG+LUN tuples in
> order to perform their SCSI multipath recovery.
> The latter does this
> and determines recovery logic using SCSI level SPC
> opcodes to test for
> nexus establishment.
>
> Connection recovery at the iSCSI level can make this
> happen very quickly
> by detecting NOP response timeouts, link layer
> failures, TCP connection
> resets and all types of ERL=1 events. So ERL=2 is
> benefical for all
> types of storage devices (drives, tapes, CD/DVD
> roms) and allows less
> reliable links (think wireless) to continue iSCSI IO
> operation in the
> face of communication path failures and resets.
>
> Thanks :-) !
>
> Oh btw, core-iscsi is alive
It would be nice if it got more publicity. I was
under the impression (as I believe a lot of other
people are as well), that it was discontinued.
> , it is currently in
> stable release and
> accepting feature requests. Please check out the
> following wiki entry
> for more information:
>
>
http://www.linux-iscsi.org/index.php/Core-iscsi_Interopt
>
> Nicholas A. Bellinger <nickb@xxxxxxxx>
Nicholas, have you performed any benchmarks between
IET and PyX or between PyX and other iSCSI targets?
If so, could you share them with the rest of us,
including the configurations used? Finally, I
couldn't find much about PyX on your site:
(http://www.sbei.com/index.php/products/iscsi/) Does
it come with a management interface? How is it priced
(per connection like WinTarget or per server)?
Thanks for your help.
Regards,
Rik Herrin
> > > > On Sun, 2006-02-26 at 07:54 -0800, Rik Herrin
> wrote:
> > > > > Thanks for your reply Ming. I understand
> that PyX
> > > > > supports erl=2, but is it really important?
> If you
> > > > > use HeaderDigest and BodyDigest (CRC32C) and
> since
> > > > > iSCSI uses TCP, doesn't that take care of
> most errors?
> > > > > I read the following: "However, just about
> every
> > > > > vendor I questioned dismisses iSCSI error
> recovery
> > > > > level 2 as unnecessary, at least for the
> time being,
> > > > > because the protocol is already built on a
> robust
> > > > > networking transport such as TCP, which
> already
> > > > > guarantees data delivery and provides error
> checking.
> > > > > [Sep. 2004]" "Nevertheless, many agree
> that iSCSI
> > > > > error recovery level 2 could be useful in
> some cases.
> > > > > For example, in case of errors, when the
> target device
> > > > > is a tape, level 2 would allow the operation
> to
> > > > > continue without having to restart."
> > > > >
>
(http://www.infoworld.com/article/04/09/03/36storinside_1.html
> > > > > ) So isn't erl=2 only really useful for
> things such
> > > > > as tapes? Wouldn't the initiator also have
> to support
> > > > > it? How many initiators currently support
> erl=2? I
> > > > > read that PyX used to have an initiator
> (core-scsi)
> > > > > but that it's been discontinued. Thanks for
> your
> > > > > input.
> > > > >
> > > > >
> > > > > --- Ming Zhang <mingz@xxxxxxxxxxx> wrote:
> > > > >
> > > > > > as far as i know, there is no such
> comparison yet.
> > > > > >
> > > > > > feature wise, pyx support erl=2, mc/s. it
> run faster
> > > > > > (not sure how much)
> > > > > > on better HW like 10G.
> > > > > >
> > > > > > ming
> > > > > >
> > > > > >
> > > > > > On Sat, 2006-02-25 at 06:09 -0800, Rik
> Herrin wrote:
> > > > > > > Hi,
> > > > > > > I was wondering if anyone had made a
> comparison
> > > > > > > between the IET target in comparison
> with
> > > > > > WinTarget
> > > > > > > and PyX? I was thinking in terms of
> features,
> > > > > > > performance, RFC compatibility, etc.
> Thanks for
> > > > > > your help.
> > > > > > >
> > > > > > >
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