[Pc_Support] Re: 68-pin SCSI card for Linux box .... -- Ultra80 (Ultra2) SCSI

[Bryan J. Smith]

On Tue, 2006-06-27 at 07:34 -0500, William A. Mahaffey III wrote:
> .... I am adding an internal HH LTO-1 (IBM 24P2401) tape drive to my P4 
> Linux box, SuSE 9.2, box-stock. I need to add a SCSI card to connect to 
> the tape drive. I see an Acard PCI 68-pin SCSI card on NewEgg, about 
> $70.00, w/ cable, but it only explicitly mentions Mac boxen for 
> compatibility. I thought *all* SCSI cards were pretty much 
> supported/would-work under Linux.

Work, maybe.  Boot, no.  It all depends.  The firmware will _not_ work
on a PC -- which means it might not setup devices correctly at POST.

> Does anyone have any reasons to rule out use of this card ? If so,
> what would you use instead (I'm shopping compatibility & price) ?
> Thanks in advance.

I can't pull it up from NewEgg.COM (NewEgg.COM has been very slow for me
the last week).

- LTO drive and SCSI signaling/speed requirements

LTO-1 requires an Ultra80 (Ultra2) SCSI card, which can be standard
32-bit PCI.

LTO-2 requires an Ultra160 (Ultra3) SCSI card, which is typically PCI-X
or 64-bit PCI, maybe 66MHz/32-bit PCI.

LTO-3 recommends an Ultra320 (Ultra4) SCSI card, which is almost always
PCI-X (or 66MHz/64-bit PCI), although newer PCIe x4 cards (_not_ x1)
might be an option now.  Now I've seen some LTO-3 drives that just spec
Ultra160, so you might not need Ultra320.

Do _not_ buy anything less or you'll kill your performance.

- LVD (Ultra80/160/320) cabling and termination

Also remember that you need to use Low Voltage Differential (LVD)
cabling and terminators.  LVD cables are _twisted_pair_, and the LVD
terminators terminate 2x as many lines as standard Single Ended (SE)
terminators.  And do _not_ confuse LVD with High Voltage Differentiate
(HVD)!

The symbols for each can be seen at the bottom of page:  
  http://scsifaq.paralan.com/scsifaqanswers4.html  

The "outer" less than bracket (<) is HVD.  Remember it's on the
"outside" of the normal SE SCSI.

The "inner" less than bracket (<) is LVD.  Remember that it's on the
"inside" of the normal SE SCSI (and SE SCSI voltage compatible).

BTW, you virtually _never_ see "pure" LVD SCSI.  You _always_ have the
"dash" because LVD is almost _always_ implemented as SE SCSI compatible.

Ironically enough, HVD SCSI is _never_ SE compatible, so it shouldn't
have that "dash" -- but it does.  HVD pre-dates LVD, so they didn't
think of this fact.

- Chipsets:  Stick with LSI Logic (fka Symbios Logic)

As far as chipsets, you can't go wrong with LSI Logic (fka Symbios
Logic).  A lot of different OEM/vendors use those chips.  _Avoid_
Adaptec (don't get me started).  Also note that Advansys (the first SCSI
vendor to support Linux back in 1994) drivers haven't been updated for
awhile, and last time I checked, they were marked "legacy" in kernel
2.6.

The 53c895 (as well as dual-channel 53c896) is Ultra80.  I bought some
Symbios Logic 53c895 32-bit PCI cards for $10 a couple months back --
and they work well!  Let me see here ... yep, they still got them too -
brand new, _not_ pulls, although OEM/non-boxed:  
  http://www.etech4sale.com/products/partinfo-id-143694.html  

They are 5V-only 32-bit PCI cards.  If you need 3.3V, they actually have
these "pulls" (not new) that are 3.3V with 5V tolerance for $33:  
  http://www.etech4sale.com/products/partinfo-id-1137.html  

The Symbios Logic 53c1010 is a dual-channel Ultra160 and are typically a
bit more, plus you do _not_ want to put them in a standard 32-bit PCI
slot (bottleneck).  It was renamed by LSI Logic as the 21040.  There are
also newer LSI Logic models as well, like the 20160, 22160, etc...

Froogle has some outstanding deals listed for $50+ on Ultra160 and
Ultra320 cards:  
  http://froogle.google.com/froogle?q=LSI+Ultra160&scoring=p  
  http://froogle.google.com/froogle?q=LSI+Ultra320&scoring=p  

Note they'll almost _always_ be 64-bit PCI or PCI-X for Ultra160/320.

Some maybe pulls, some may be new OEM, etc...  Also note that some have
_Sun_ OpenFirmware, and _not_ PC firmware.  But they typically charge
and arm'n a leg for those anyway -- so most low-cost cards are PC.

- Final note on performance

*DO*NOT* put a LTO-1 card on a system in a 32-bit slot when your storage
is _also_ on the same 32-bit bus.  You're going to _saturate_ your
32-bit PCI -- 133MBps _theoretical_ maximum -- bus.  Because you're
first going to send 40+MBps from the disk to memory, and then another 40
+MBps from memory to tape.  Not good to be "butting up" against that
limitation.

Try to put storage and tape on _separate_ PCI-X busses.  Alternatively,
this could be newer PCIe channels or chipsets with SATA on dedicated
PCIe x1/x4 channels or HyperTransport bridges (in the chipset itself).


-- 
Bryan J. Smith           Professional, technical annoyance
mailto:b.j.smith at ieee.org     http://thebs413.blogspot.com
----------------------------------------------------------
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