Uses for a couple boxes full of Compaq 2.1gig Fast-Wide SCSI2?

[mikebw at bilow.bilow.uu.ids.net (Mike Bilow)]

Mark Spencer wrote in a message to Mike Bilow:

 MS> I recently got approximately twenty of these drives back after 
 MS> an organization wide upgrade of our Vines servers. Rather than 
 MS> surplus them, I'm wondering what use they would be on a PC? I'm 
 MS> not very familiar with the SCSI architecture, but I would 
 MS> assume these drives would outperform an IDE setup by a 
 MS> significant margin, especially on a system under heavy load. 

SCSI has theoretical advantages over IDE, especially when lots of devices are
running together, in that there can be much less demand on the main CPU. 
However, in practice, old SCSI drives may be slower than new IDE drives.

 MS> Is SCSI2 limited to eight devices? I'm wondering if I could 
 MS> install eight (or more?) of these drives on a 486/100 (ISA) or 
 MS> Pentium 75 (PCI) running linux and try and then I'll try to 
 MS> justify to my coworkers why there are cables and drives snaking 
 MS> out into the hallway. ;)

You are limited to eight Narrow (8-bit) devices per physical SCSI bus, but one
of these is the controller.  With Wide (16-bit) devicees and cabling, you can
have up to 16 devices per bus, including the controller.  Some controller cards
have more than one physical bus, such as the Adaptec AHA-2742T EISA controller
or the AHA-3940 PCI controller.  You can also use multiple controller cards per
machine, up to the limit of slots available.

 MS> Any ideas for applications? I imagine this would be an 
 MS> excellent fileserver for my local office .. Or possibly setup 
 MS> some kind of proxy to increase the speed that people "access" 
 MS> the web?

You could also run software RAID with this many drives, which might be wise.

 MS> What would recommended SCSI2 fast-wide ISA or PCI adapters be?  
 MS> Do the Adaptec's work well with linux?

Most Adaptec controllers are pretty good, but there is a lot of reverse
engineering involved and this means that some of the newer chipsets are harder
to get to work correctly.  If I were buying a new SCSI controller knowing that
I was going to be using it under Liunx, I would probably choose Mylex/Buslogic.
 The Adaptec AHA-2940 series is fairly stable under Linux at this point, as
long as you use recent (2.2) kernels and do not get the type with low-voltage
differential connections.
 
-- Mike


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