Mylex/Compaq RAID controller placement in config

Mylex/Compaq RAID controller placement in config

[Roy Sigurd Karlsbakk]

hi

I apologize if this is a well-stressed question, but why is the Mylex and
Compaq RAID controllers placed under 'Block devices' rather than under
'SCSI'?

thanks

roy

---
Roy Sigurd Karlsbakk, MCSE, MCNE, CLS, LCA

Computers are like air conditioners.
They stop working when you open Windows.

Re: Mylex/Compaq RAID controller placement in config

[Alan Cox]

> I apologize if this is a well-stressed question, but why is the Mylex and
> Compaq RAID controllers placed under 'Block devices' rather than under
> 'SCSI'?

Because they are ?

They dont provide scsi as the native interface (nor do some of the others
but thats a seperate saga)

Re: Mylex/Compaq RAID controller placement in config

[Roy Sigurd Karlsbakk]

> Because they are ?
>
> They dont provide scsi as the native interface (nor do some of the others
> but thats a seperate saga)

I know it might seem silly, but as to make things clearer for most
users/admins, wouldn't it be better to just call them SCSI controllers, as
they all indeed connect SCSI drives to the host?

roy

---
Roy Sigurd Karlsbakk, MCSE, MCNE, CLS, LCA

Computers are like air conditioners.
They stop working when you open Windows.

Re: Mylex/Compaq RAID controller placement in config

[Arjan van de Ven]

Roy Sigurd Karlsbakk wrote:
> 
> > Because they are ?
> >
> > They dont provide scsi as the native interface (nor do some of the others
> > but thats a seperate saga)
> 
> I know it might seem silly, but as to make things clearer for most
> users/admins, wouldn't it be better to just call them SCSI controllers, as
> they all indeed connect SCSI drives to the host?

They're not SCSI _controllers_. They happen to like scsi drivers, but
there's nothing 
scsi about the controller. and admins would expect all controllers from
the
"SCSI Controllers" menu to show up as /dev/sda etc, which these don't.

> ---
> MCSE, MCNE, CLS, LCA

Maybe this explains it ;)

Re: Mylex/Compaq RAID controller placement in config

[Alan Cox]

> > They dont provide scsi as the native interface (nor do some of the others
> > but thats a seperate saga)
> 
> I know it might seem silly, but as to make things clearer for most
> users/admins, wouldn't it be better to just call them SCSI controllers, as
> they all indeed connect SCSI drives to the host?

Well we could simplify it further by putting all configuration options under
a single menu called "things". The controllers under block dont have drives
appearing as /dev/sd*

Re: Mylex/Compaq RAID controller placement in config

[Venkatesh Ramamurthy]

> I know it might seem silly, but as to make things clearer for most
> users/admins, wouldn't it be better to just call them SCSI controllers, as
> they all indeed connect SCSI drives to the host?

Eventhough they connect SCSI Drives, the fact is that they are totally
different beast from the OS/driver perspective.

Re: Mylex/Compaq RAID controller placement in config

[Ricky Beam]

On Tue, 6 Nov 2001, Roy Sigurd Karlsbakk wrote:
>I know it might seem silly, but as to make things clearer for most
>users/admins, wouldn't it be better to just call them SCSI controllers, as
>they all indeed connect SCSI drives to the host?

No!  That would actually increase the confusion.  You can connect almost any
SCSI device to the Mylex RAID controller, but you won't be able to use
anything that isn't a drive configured through the controller. (There's a
DOS ASPI driver to let you see a CDROM on the bus, but that's only there
for installation support.)

If you list the RAID controller as a SCSI device, people *will* think they
can plug any SCSI device they have onto it and be able to use it.  Well,
they cannot (and never will.)  Additionally, nothing the driver provides
lives under /dev/{sd,st,sg}* and you have ZERO SCSI layer access through
the driver.

--Ricky

RE: Mylex/Compaq RAID controller placement in config

[Dana Lacoste]

> Well we could simplify it further by putting all
> configuration options under a single menu called
> "things". The controllers under block  dont have
> drives appearing as /dev/sd*

I can understand the initial complaint, but I think it
comes down to a problem of user vs. developer :

For example : All of the SCSI devices are block devices,
aren't they?  So how come they're not under "block devices"
in the menu?

All of the devices under "block devices" are storage controllers
(or ways of accessing storage in linux) so how come they're not
listed as such in the menuconfig options?

and then you hit the whole I20 problem.  Half my raid controllers
aren't under either of those two menus.

Maybe ESR's config method would allow for a way of presenting the
menus in different ways?  One for developers (who care more about
the subsystems and how they're connected) and one for users, who
care more about what the device does then how it's written?

--
Dana Lacoste       Linux Developer
Peregrine Systems   Ottawa, Canada

Re: Mylex/Compaq RAID controller placement in config

[Alan Cox]

> and then you hit the whole I20 problem.  Half my raid controllers
> aren't under either of those two menus.

I2O is a tricky one - the fusion mpt stuff too. I've not found a better
answer for that

RE: Mylex/Compaq RAID controller placement in config

[Richard B. Johnson]

On Tue, 6 Nov 2001, Dana Lacoste wrote:

> > Well we could simplify it further by putting all
> > configuration options under a single menu called
> > "things". The controllers under block  dont have
> > drives appearing as /dev/sd*
> 
> I can understand the initial complaint, but I think it
> comes down to a problem of user vs. developer :
> 
> For example : All of the SCSI devices are block devices,
> aren't they?  So how come they're not under "block devices"
> in the menu?
> 

No, we have (Americal National Standard X3.131-1986) "sequential-access",
"printer", "processor", etc., SCSI devices. They are controlled using a
"command-block", however they are not "block" devices although the 
sequential-access device could be (like tape). My tape is /dev/st0, it's
a character device.

Cheers,
Dick Johnson

Penguin : Linux version 2.4.1 on an i686 machine (799.53 BogoMips).

    I was going to compile a list of innovations that could be
    attributed to Microsoft. Once I realized that Ctrl-Alt-Del
    was handled in the BIOS, I found that there aren't any.

RE: Mylex/Compaq RAID controller placement in config

[Ricky Beam]

On Tue, 6 Nov 2001, Dana Lacoste wrote:
>For example : All of the SCSI devices are block devices,
>aren't they?  So how come they're not under "block devices"
>in the menu?

Nope.  They present a hardware interface to various devices.  Some of those
devices are block devices, but not all of them (eg. tape drives, scanners,
printers, SCSI-IP :-))

>All of the devices under "block devices" are storage controllers
>(or ways of accessing storage in linux) so how come they're not
>listed as such in the menuconfig options?

Because they aren't.  Alot of the structure is historical... 15 years ago,
all you could plug into IDE were block devices and there you are.

>and then you hit the whole I20 problem.  Half my raid controllers
>aren't under either of those two menus.

Heh, well, I2O is it's own problem. (And it's eye-two-oh, not zero.) In
most respects, I2O is more like "pci support" than a "driver" per se. (It's
just one more layer.)

--Ricky

Re: Mylex/Compaq RAID controller placement in config

[Stephen Cameron]

Venkatesh Ramamurthy wrote:

> > I know it might seem silly, but as to make things clearer for most
> > users/admins, wouldn't it be better to just call them SCSI controllers, as
> > they all indeed connect SCSI drives to the host?
> 
> Eventhough they connect SCSI Drives, the fact is that they are totally
> different beast from the OS/driver perspective.

Actually, at least in Alan Cox's tree, the cciss driver is BOTH a SCSI driver
and a block driver simultaneously, or can be configured that way anyhow.  That
change was intruduced for the sole purpose of accessing SCSI tape drives via
array controllers.  (nevermind why you'd want to do that, suffice it to say,
some folks want this ability.)  I would consider it mostly a block driver, even
when SCSI tape drive support is compiled in.

In any case, the "drives" (logical volumes) which are presented by the
hardware/firmware and eventually by the driver to the OS do not in general
correspond 1-to-1 with physical SCSI drives.  Even the SCSI busses presented by
the cciss driver with SCSI tape support do not necessarily correspond with
physical SCSI busses, so considering these controllers "SCSI controllers" is
not really accurate, though typically they _contain_ what you can think of as
one or more SCSI controllers as part of the back-end, which the firmware uses
to control SCSI devices,.  Though, in some cases it could be a fibre-channel
back-end instead of SCSI.  In any case, the nature of the back-end is
irrelevant to the driver for purposes of doing i/o to logical volumes.

Incidentally, last time I checked, Linus' tree contained the documentation
portion of the patch which allowed a cciss controller to access SCSI tape
drives (Documentation/cciss.txt) but none of the actual code that implemented
that functionality... :-/  oh well.

-- steve (aka steve.cameron@compaq.com)

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