Wide negotiation fails with 80->68 LVD adapter?

Wide negotiation fails with 80->68 LVD adapter?

[Alexy Khrabrov]

Greetings -- did anybody try to connect a SCSI SCA
hard drive (with 80 pins) to an Adaptec 7899
Ultra160 with 65 pins?  Mine seems unable to spin
them at 160 Mbps.

I'm running Linux, Suse 7.2 _ many upgrades,
kernel 2.4.20-pre9, with Adaptec 7899, v25113 in
SCSISelect.  My system came with a Barracuda ...LW
drive, 68 pin, and it was always working fine in
160 Mbps mode.

A week ago, I got some more Barracudas on ebay, those
were SCA ones, ...LC, so I got an 80->68 LVD adapter.
Here it is, I guess there's only one, as everybody
resells this one:

http://www.scsistuff.com/106-0067.htm

Here's the Barracuda:
http://www.seagate.com/support/disc/specs/scsi/st150176lc.html
Strangely, it comes up as SX..., not ST..., in
Adaptec's bootup.

I set only the SCSI IDs on my Barracudas.  OK.

The first thing after Dell splash which comes during
boot is SCSI list, and my good ol' LW Barracuda comes
up first ith SCSI 0 and 160 speed.  Good.  But the two
new ones came up as ASYN!  SCSISelect would hang, with
SCSI device 1 (a new Barracuda) LED lit, until I
switched them in SCSIselect to ASYN.  And then they
negotiated a wonderful speed of 6.6 Mbps, just above
my dds tape...

Since the idea for these was to keep my DVD images,
5 GB each, waiting was not an option -- and the best
thing I could do is to disable Wide Negotiation, => OFF,
and choose maximum 40 Mbps in SCSIselect for the LCs.
Works, but now I wonder what should I do to spin them
at 160?  Is it

-- Adaptec 7899 firmare/Dell BIOS?
-- 80->68 adapter settings (looks like none is needed,
   setting SYN jumper did nothing, looks like it's a
   different kind of syncing -- for spindles)
-- Barracuda's jumpers (now that adapter takes over ID,
   I wonder if any other would matter; and ddefaults are
   to be the fastest)
-- Linux aic7xxx driver
-- Linux higher-level SCSI driver(s)?
-- Something else is fishy?

Any hints would be highly appreciated!

Cheers,
Alexy

Re: Wide negotiation fails with 80->68 LVD adapter?

[Doug Ledford]

On Mon, Oct 21, 2002 at 01:14:47AM -0400, Alexy Khrabrov wrote:
> 
> Greetings -- did anybody try to connect a SCSI SCA
> hard drive (with 80 pins) to an Adaptec 7899
> Ultra160 with 65 pins?  Mine seems unable to spin
> them at 160 Mbps.

[ snip long description ]

There is no difference between 68 pin drives and 80 pin drives as far as 
the controller and the drive are concerned.  It's all just a physical 
interconnect difference.  The problem you are describing is a 
non-functional SCA->wide adapter.  I have yet to ever find a simple 
wide<->SCA adapter that worked.  I've always had to have a real SCA 
backplane before things worked properly.

-- 
  Doug Ledford <dledford@redhat.com>     919-754-3700 x44233
         Red Hat, Inc. 
         1801 Varsity Dr.
         Raleigh, NC 27606
  

Re: Wide negotiation fails with 80->68 LVD adapter?

[Alexy Khrabrov]

On Mon, Oct 21, 2002 at 12:34:24PM -0400, Doug Ledford wrote:
> On Mon, Oct 21, 2002 at 01:14:47AM -0400, Alexy Khrabrov wrote:
> > 
> > Greetings -- did anybody try to connect a SCSI SCA
> > hard drive (with 80 pins) to an Adaptec 7899
> > Ultra160 with 65 pins?  Mine seems unable to spin
> > them at 160 Mbps.
> 
> [ snip long description ]
> 
> There is no difference between 68 pin drives and 80 pin drives as far as 
> the controller and the drive are concerned.  It's all just a physical 
> interconnect difference.  The problem you are describing is a 
> non-functional SCA->wide adapter.  I have yet to ever find a simple 
> wide<->SCA adapter that worked.  I've always had to have a real SCA 
> backplane before things worked properly.
> 

Thanks Doug.  Justin Gibbs concurred.  I am wondering whether the curse
is complete or anybody could recommend an adapter/enclosure?  I was
googling around and found things like CRU dataport racks, InClose 
external enclosures, and cremax racks, all having a 80<->68 model.
Now these things looks like more professional, and at least there's
a manufacturer as opposed to the anonymous Taiwan-made 80<->68 adapter.
Any experience with any of these stuffed with SCA drives connected to
a 68 pin Ultra160?...
-- 
Cheers,
Alexy Khrabrov :: www.setup.org :: Age Quod Agis

Re: Wide negotiation fails with 80->68 LVD adapter?

[Dan Jones]

Alexy Khrabrov wrote:
> 
> Thanks Doug.  Justin Gibbs concurred.  I am wondering whether the curse
> is complete or anybody could recommend an adapter/enclosure?  I was
> googling around and found things like CRU dataport racks, InClose
> external enclosures, and cremax racks, all having a 80<->68 model.
> Now these things looks like more professional, and at least there's
> a manufacturer as opposed to the anonymous Taiwan-made 80<->68 adapter.
> Any experience with any of these stuffed with SCA drives connected to
> a 68 pin Ultra160?...
> --

Search for Corporate Systems Center (CSC) part "sca2lvd". Anything 
else and you are on you own.

-- 
Dan Jones           "'Tis hard to say, if greater want of skill
                     Appear in writing or in judging ill;
                     But of the two, less dangerous is th' offence 
                     To tire our patience, than mislead our sense." Pope

Re: Wide negotiation fails with 80->68 LVD adapter?

[Alexy Khrabrov]

While I'm on this 80<->68 pins subject, or How to Accomodate
SCA drives, I wonder what SCA backplane means.  Is it the
complete SCSI system starting with the controller?  Then it
has to have 80 pin internal connector?  And Adaptec should
have it?  But all Adaptec cards, including Ultra320, are
68 pin internal/external...  I'm a bit confused.  Is there
such a thing as 80 pin SCA, PCI SCSI card?  With an 80 pin
SCA ribbon inside?  Can you guys recommend some good ones?
Getting a PCI SCSI card is an alternative to getting an 
external enclosure...  Interesting options...

-- 
Cheers,
Alexy Khrabrov :: www.setup.org :: Age Quod Agis

Re: Wide negotiation fails with 80->68 LVD adapter?

[Dan Jones]

Alexy Khrabrov wrote:
> 
> While I'm on this 80<->68 pins subject, or How to Accomodate
> SCA drives, I wonder what SCA backplane means.  Is it the
> complete SCSI system starting with the controller?  Then it
> has to have 80 pin internal connector?  And Adaptec should
> have it?  But all Adaptec cards, including Ultra320, are
> 68 pin internal/external...  I'm a bit confused.  Is there
> such a thing as 80 pin SCA, PCI SCSI card?  With an 80 pin
> SCA ribbon inside?  Can you guys recommend some good ones?
> Getting a PCI SCSI card is an alternative to getting an
> external enclosure...  Interesting options...
> 

SCA stands for single connnector attachment. It is a super-set
of the 68-pin connector and includes power and ID pins. It was 
designed to allow SCSI drives to be plugged into backplanes. 
There aren't any SCA cables or SCA/PCI cards.

-- 
Dan Jones           "'Tis hard to say, if greater want of skill
                     Appear in writing or in judging ill;
                     But of the two, less dangerous is th' offence 
                     To tire our patience, than mislead our sense." Pope

Re: Wide negotiation fails with 80->68 LVD adapter?

[Alexy Khrabrov]

Dan -- thanks.  I see those sca2lvd are mentioned as working by others
trapped in SCA to 68 pin LVD switching.

So what is a "backplane"?  I admit I'm ignorant and never saw one, just
curious.  If it's basically a back of a rack, and there's no 80 pin bus,
then it's just an enclosure with its own 80<->68 adapter, right?

-- 
Cheers,
Alexy Khrabrov :: www.setup.org :: Age Quod Agis

Re: Wide negotiation fails with 80->68 LVD adapter?

[Doug Ledford]

On Tue, Oct 22, 2002 at 12:16:44PM -0400, Alexy Khrabrov wrote:
> 
> Dan -- thanks.  I see those sca2lvd are mentioned as working by others
> trapped in SCA to 68 pin LVD switching.
> 
> So what is a "backplane"?

If you look inside one of the Dell servers that use SCA drives, or inside 
any external drive enclosure that uses SCA drives, they will have a green 
board that the drive sockets are all attached to and which is the carrier 
of the signals to all the drives.  That board is the backplane.  The 
primary difference between a backplane and a simple LVD<->SCA adapter is 
that backplanes are usually semi-intelligent devices themselves that don't 
just connect the drives to the SCSI bus, but in many cases have built in 
termination for the 68 pin LVD connection that is then routed into a 
bridge chip for the SCSI bus and then the other side of that bridge chip 
is then routed to the SCSI bus built into the backplane.  In that sense 
you have two SCSI busses and a smart bridge that connects them instead of 
being like the simple adapter which simply sticks the drive on the 
existing SCSI bus.  Keep in mind one of the things that determines bus 
quality is something called "stub length".  That's the total length of the 
various SCSI lines from the point at which they leave the primary SCSI bus 
until they terminate at the end point SCSI chip.

  SCSI Cable, terminator at end
      ^
      | __Stub Length__
      |/               \
      --+---+------------|
      | |   |            SCSI chip on drive
      | |   Connector on drive
      | LVD<->SCA Adapter
      |
      |
      
As you can see by my pitiful ASCII art, the stub length gets longer when
you plave an LVD<->SCA adapter between the drive and the 68 pin connector
on the cable.  Depending on the SCA adapter and the drive in question, you
could actually be increasing the stub length by a full 100%.  That
degrades the whole bus.  With backplanes, by putting all of the SCA
connectors directly on the backplane and running the SCSI bus through the
backplane instead of a cable, they can guarantee good signal quality.  By
using a bridge chip between the internal backplane and the external SCSI
cable, they again guarantee good signal quality inside the chassis
(because any possible poor signal traits on the external SCSI cable are
entirely electrically isolated away from the internal bus), and they also
guarantee that the signal quality on the external SCSI cable will not be
degraded by the internal signal traces since they are, again, totally
electrically isolated.  Of course, not all backplanes use electrical
isolation of the internal and external SCSI busses like this.  But, even 
without it, just having the connectors and the SCSI bus itself both inside 
of a printed circuit board instead of attached to a cable helps them 
control overall signal quality.


-- 
  Doug Ledford <dledford@redhat.com>     919-754-3700 x44233
         Red Hat, Inc. 
         1801 Varsity Dr.
         Raleigh, NC 27606
  

Re: Wide negotiation fails with 80->68 LVD adapter?

[Alexy Khrabrov]

On Tue, Oct 22, 2002 at 01:03:16PM -0400, Doug Ledford wrote:
> [...] just having the connectors and the SCSI bus itself both inside 
> of a printed circuit board instead of attached to a cable helps them 
> control overall signal quality.

Doug -- thanks for the excellent explanation and a great diagram!
Now it's all clear.  Alas, I don't have a backplane or a place to
stick one to, so I ordered a few recommended sca2lvd adapters --
the one Dan Jones referred to was reported "good" on comp.periphs.scsi
is by Corpsys:

http://www.corpsys.com/store/prodinfo.asp?number=SCA2LVD&variation=&aitem=24&mitem=82

and I also used to like excellent stuff from cablemakers.com, which
is the best place I saw so far for all things SCSI if more expensive --
but those folks put up all the right photos, very professional.  I also
am going to get another adapter from scsisource.com, all different
from the high-bit-squashing Taiwanese piece of art "v1.1" others resell...
I'll report my findings here!

--
Cheers,
Alexy Khrabrov :: www.setup.org :: Age Quod Agis

Re: Wide negotiation fails with 80->68 LVD adapter?

[Alexy Khrabrov]

OK, I've got the CSC (Corpsys) "sca2lvd" adapters and tried them
with my Barracuda ST150176LC's.  The adapters look much more solid
than the anonymous Taiwan-made "v1.1" ones.  The CSC adapters have
two ig red LEDs onboard, the inner part of the circuit board
has a cover, etc.  

However, they too failed to spin my drives at 160, only at 80.
I went back and enabled Wide Negotiation, then trying
to set speed at 160 caused Adaptec 7899 to recognize
the drives as ASYN, hangup, decreasing it to 80 led to their
recognition as 80 and working fine.  

I went back and tried the "v1.1" adapters in that setting,
Wide Negotiation enabled, 80 sync speed, and they worked
at the same speed (as measured by copying a 5 GB from
the 160 drive).  Doh.

So I reread the drive manual, which says that 
Barracuda 50 drives support ANSI SCSI, SCSI-2 and SCSI-3
(Fast-20 and Fast-40), which it says are the same
as Ultra-1 and Ultra-2 for Fast-20/40, respectively.
Mysteriously, Ultra2 is referred to as Ultra80 elsewhere,
so looks like Fast-40 _is_ 80?  If SCSI veterans could
clarify this, I'd see how 40=80...  Especially, given
aic7xxx says something about 80 (40 MHz) in parentheses...

In all cases, seems that it's really the drive, Barracuda 50
family is Ultra2 <=> Ultra80 (right?) but I was able to
enable Wide Negotiation and set speed to 80, and aic7xxx v6.2.8
showed them registered at 80.  I'm just curious if I still could
kinda spin them up to 160 anyways...  :-)

Hence, so far, both SCA<->68 LVD adapters worked as advertised.
I'm going to get a real 160 SCA drive and test it further.
In the same vein, if I do end up getting an Ultra 320 card,
and I will get an Adaptec one, what should I look for in the
drive to see if it's capable of supporting 320?  I'm interested
in Ultra160 drives, usually SCA ones I can get at closeouts,
but I heard (in the Ultra320 thread) that they can spin at 320
in case they support "HBA" -- can someone please elaborate?

Many thanks, I'll put together a SCA<->68 mini-HOWTO based 
on this.

-- 
Cheers,
Alexy Khrabrov :: www.setup.org :: Age Quod Agis

Re: Wide negotiation fails with 80->68 LVD adapter?

[Doug Ledford]

On Sat, Oct 26, 2002 at 10:53:09AM -0400, Alexy Khrabrov wrote:
> 
> So I reread the drive manual, which says that 
> Barracuda 50 drives support ANSI SCSI, SCSI-2 and SCSI-3
> (Fast-20 and Fast-40), which it says are the same
> as Ultra-1 and Ultra-2 for Fast-20/40, respectively.
> Mysteriously, Ultra2 is referred to as Ultra80 elsewhere,
> so looks like Fast-40 _is_ 80?  If SCSI veterans could
> clarify this, I'd see how 40=80...  Especially, given
> aic7xxx says something about 80 (40 MHz) in parentheses...

You aren't paying attention to the units of measure.  The 40 in
Ultra2/Fast40 is 40MHz (aka, 40 million cycles per second).  The SCSI bus
itself is either narrow (8 bits) or wide (16 bits).  The speed rating you
are referring to is in Mega*BYTES* per second.  So, to get the total
speed, you multiply the frequency of data transfer (the MHz part) times
how many bytes are transferred in each data transfer operation (aka, there
are 8 bits per byte, so a narrow bus transfers exactly one byte of
information in each transfer cycle, while a wide bus transfers 2 bytes of
information in each cycle).  So, a Wide (16 bit, 2 byte) bus operating at
40MHz transfer frequency is actually transferring data at a rate of 80
MegaBytes of data per second.

> In all cases, seems that it's really the drive, Barracuda 50
> family is Ultra2 <=> Ultra80 (right?) but I was able to
> enable Wide Negotiation and set speed to 80, and aic7xxx v6.2.8
> showed them registered at 80.  I'm just curious if I still could
> kinda spin them up to 160 anyways...  :-)

No.  A drive will *only* do what it is capable of doing, there is no
margin there for overclocking (and in fact the negotiation protocol won't
allow it, on most 80MByte/s drives if you set the Adaptec BIOS to
160MByte/s, the card and drive will still end up at 80MByte/s anyway
because the drive firmware and the controller driver have a message
protocol that they follow to negotiate the best possible speed that both
of them support and obviously if the drive only supports 80MByte/s
transfers, then that's the best that both of them support, but in your
case the drive appears to be locking up during the transfer speed
negotiation phase which could be the fault of the linux scsi driver you
are using or the fault of the drive firmware).

> Hence, so far, both SCA<->68 LVD adapters worked as advertised.
> I'm going to get a real 160 SCA drive and test it further.
> In the same vein, if I do end up getting an Ultra 320 card,
> and I will get an Adaptec one, what should I look for in the
> drive to see if it's capable of supporting 320?

The card and the drive *both* have to support 320 speeds, and you have to 
have a driver for the 320 card.  Justin Gibbs has a driver for the adaptec 
320 cards, but it isn't in all the stock linux kernels yet (I think it's 
in 2.4.19 and later, and should be in the 2.5 kernel series pretty soon).

-- 
  Doug Ledford <dledford@redhat.com>     919-754-3700 x44233
         Red Hat, Inc. 
         1801 Varsity Dr.
         Raleigh, NC 27606