Adaptec 7890 and RAID portIII RAID controller Linux Support

[Robert G. Brown]

On Thu, 25 Feb 1999, Doug Ledford wrote:

> > Would a reasonable solution be to use a single IDE disk as a boot/swap
> > disk and reserve the SCSI channel(s) for striping or RAID as you
> > describe?  I've experience a little bit of weirdness running IDE and
> > SCSI in the same system, but it might have been hardware mediated
> > weirdness.
> 
> That's possible, but what I've found to be a good method is to do something
> like this:
> 
> /dev/sda1: 200MB
> /dev/sda2: Rest of disk
> 
> Then I copy that exact same paritioning to all the rest of the disks.  When I
> actually lay it out, /dev/sda1 becomes the self sustaining /boot partition and
> /dev/sdb1, /dev/sdc1, /dev/sdd1, etc all become identical swap partitions that
> are all set up with exactly the same priority level in the fstab.  This way,
> all the swap partitions end up being their own psuedo raid stripe, but they
> bypass the VFS code and go directly into the block driver.  They are also
> fairly small partitions by total drive standards and are located in the front
> of the disk close to the RAID partitions so that you avoid the long seek
> problem I mentioned when you split a disk into several larger chunks.  That's
> about as close as you can get to the absolute maximum performance of the array
> while not using a dedicated SCSI disk or IDE disk.  It also drastically
> increases swap performance.

Consider this a part of my future server recipes.

> There is a second reason for this as well.  I've identified at least one area
> of problems in the mid-level SCSI code, and that involves locking between two
> totally different scsi low level drivers (in this case, BusLogic and
> aic7xxx).  I have a system were I can reliably produce lockups and other
> errors by mixing the two brands of controllers and drivers, but where either
> one by themselves works fine with the same setup.  Aka, 2 aic7xxx cards to
> handle the two busses works fine, 2 buslogics cards to handle the two busses
> works fine, 1 buslogic and 1 aic7xxx based cards spells problems.  This
> happens to be very high on my list of things to fix.  Unfortunately, I'm
> afraid the answer may be that it will show up in 2.3 with other mid level
> modifications.  However, since I can cite at least one system that acts this
> way reliably, I'm recommending people try and be homogeneous in the SCSI/IDE
> configuration on a single linux system for the time being.  Note, very few
> people have even considered that this might be a problem, so that gives some
> sort of indication about how many people have mixed scsi systems.  I also

I've got or run several, and some of them have ended up being enough of
a pain in the butt that we've disassembled one or the other subsystem
and moved it.  It has been extraordinarily difficult to achieve stable
bootability, for example -- sometimes one of the systems boots, runs for
a while, and dies.  Still I do have one that has run for months
perfectly happily, although it only relatively rarely uses its 2940, and
my samples are very small.  If you say I'm not alone in having problems
I'll eschew this configuration in future designs.

   rgb

Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu





To Unsubscribe: send mail to majordomo at FreeBSD.org
with "unsubscribe aic7xxx" in the body of the message