scsidisks

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Subject: Re: problems when mounting my scsi cdrom
From: Sam <sam@asatek.com>
Date: Thu, 03 Jun 1999 19:12:26 -0400

Dawid Michalczyk wrote:

> Detected scsi CD-ROM sr0 at scsi0, channel 0, id 3, lun 0
> sr0: disc change detected.
> and here is how my cdrom2 fstab entry looks:
> /dev/sr0                /mnt/cdrom2             iso9660 noauto,ro,user  0 0
> when I try to mount cdrom2 I get "special device dev/sr0 does not exist"
> 
> what should I do to mount my scsi cdrom?
 
Easy one once you know.  I had the same problem, but no one answered.  I
found it in the docs.

Use sdc0 as below at the command prompt or change sr0 to sdc0 in your
/etc/fstab:

mount -t iso9660 -r /dev/sdc0 /mnt/cdrom

It worked great!

===

Subject: RE: problems when mounting my scsi cdrom
From: Uncle Meat <kcsmart@worldinter.net>
Date: Thu, 03 Jun 1999 19:17:11 -0500 (CDT)



On 03-Jun-99 Dawid Michalczyk opined:
> SCSI cd detection problems
> 
> Just installed RH6 and have problems when mounting my scsi cdrom.
> Here is what dmesg says:
> 
> scsi : 1 host.
>   Vendor: TEAC      Model: CD-R55S           Rev: 1.0G
>   Type:   CD-ROM                             ANSI SCSI revision: 02
> Detected scsi CD-ROM sr0 at scsi0, channel 0, id 3, lun 0
> sr0: disc change detected.
> 
> and here is how my cdrom2 fstab entry looks:
> 
> /dev/sr0              /mnt/cdrom2             iso9660 noauto,ro,user 
0 0     
> 
> when I try to mount cdrom2 I get "special device dev/sr0 does not
> exist"

Mine used to say the same during boot. But, the drive was on /dev/scd0
instead. I'd try that.

===

Subject: problems when mounting my scsi cdrom
From: Kayvan Aghaiepour Sylvan <kayvan@sylvan.com>
Date: Thu, 3 Jun 1999 18:21:40 -0700 (PDT)


You can do this:

    mknod /dev/sr0 b 11 0

That should do it.

			---Kayvan
===

Subject: Re: cmd to reinitialize SCSI bus ?
From: "Jose M. Sanchez" <opjose@ex-pressnet.com>
Date: Mon, 21 Jun 1999 17:17:34 -0400

heather casler <heather=casler%eng%emchop1@fishbowl02.lss.emc.com> wrote: 

> I know it's not a good idea to pull the cable when you're
> doing I/O, but I'm doing a test and part of it is to see
> how the host will react to a cable pull and to determine
> what needs to be done to get the host back up and running
> with the least amount of down time.  For instance, what
> would the Linux host do if someone tripped over the SCSI
> cable?  I was looking for a command that could be used to
> go out and search the bus without having to reboot or
> power down the system.  Something like drvconfig in
> Solaris or vgscan in HP or scsiha in SGI....anything in
> Linux that will allow me to recover/renegotiate the SCSI
> connection without having to reboot?


The problem is that these devices are not designed to survive that type of
event.

There is no optical isolation of the lines, so often the scsi controller
itself will freeze or at best lose communication with all devices on the
SCSI chain...

Linux has no mechanism for directly dealing with a hung adapter, though it
does a pretty good job of automatically re-initing hung scsi devices if it
fails to get a response within
a predetermined amount of time...

Suffice it to say, that if someone trips over the scsi cable, the system
will need to be rebooted... after it has been powered off and all the
connections re-established...

You could potentially attempt to unload the SCSI drivers from the kernel, if
the system is not frozen, but you'll find the kernel will recognize that the
device is still mounted and prevent this. You'll also be unable to dismount
the device, since Linux will be unable to flush it's buffers... (hmm if you
get this far then maybe the SCSITOOLS might help you...)

Round and round it goes...

===

Subject: Re: cmd to reinitialize SCSI bus ?
From: "Jose M. Sanchez" <opjose@ex-pressnet.com>
Date: Fri, 18 Jun 1999 17:37:28 -0400



Not a very good idea!

At this point linux (and any OS for that matter) will be unable to dismount
filesystems
and write out any changes...

Try typing

sync;sync;sync;halt

Then shut the system off...

Plug that cable back in (THIS TIME WITH THE POWER OFF!)

And let linux fsck the drives, keep your fingers crossed, bow to the east
and west, and
say "there's no OS like Linux" three times in a row...

-JMS

===

Subject: Re: Problem Accessing SCSI Disk
From: Jan Carlson <janc@iname.com>
Date: Sun, 20 Jun 1999 00:02:39 -0400


Donnie Barnes wrote:
> 
> On 19 Jun 1999 20:09:33 -0400, Trevor Astrope <astrope@e-corp.net> wrote:
> >Hi, I recently took a system in to have the cpu upgraded and the
> >components transfered from an atx case to a rack case. When I got home,
> >the kernel booted, but e2fsck would just hang. I used a boot/rescue disk
> >and tried running e2fsck manually and it hangs again, but not before
> >outputting the following messages:
> >
> >/dev/sda1 was not cleanly unmounted,
> >check forced
> >pass 1, checking inodes, blocks and sizes
> >scsi: tagged queuing now active for target 0
> >
> >Then nothing. Does anyone know what might be causing this? Could it just
> >be that the scsi disk wasn't connected properly? All my partitions show up
> >with fdisk and the scsi bios detects the Seagate drive when the scsi bios
> >is scanned... Also the kernel boot messages show that the disk is detected
> >at scsi0.
> >
> >Any help is appreciated.
> 
> Sounds like you might be missing the termination now, or the cable got
> pinched and is now bad in some way.  It definitely sounds like a
> cabling/termination issue...

They could have connected the drives with the terminated one
not at the end of the cable, or there might be no device at
the end of the cable which is just as bad. 

Maybe they were thinking of IDE...

===

Subject: Anyone had problems with SCSI HD >= 18 GB?
From: "Steve \"Stevers!\" Coile" <scoile@redhat.com>
Date: Thu, 17 Jun 1999 12:17:15 -0400 (EDT)


I've received several reports from folks having difficulties using 18
GB and larger SCSI hard drives.  These folks *must* partition the drive:
a single, large partition will not be recognized by Linux.

Has anyone experienced this?  Anyone know anything about it?

===

Subject: Re: large SCSI HDs (>18G)
From: Ron Golan <rgolan@coalabs.com>
Date: Thu, 17 Jun 1999 15:16:42 -0700 (PDT)


On Thu, 17 Jun 1999, Matt Housh wrote:

> 
> 	No idea about drives THAT big, as I've only got a 9G, but you
> still have to observe the 1024 cylinder limit of the bios. My 9G U2W
> reports 1111 cylinders, so I have it partitioned with a small boot
> partition for kernels, that fits under the 1023rd cyl... I would assume
> that, barring bios incompatibilities, the larger drives would act the
> same...

I am using a 9.1GB SCSI drive and have some problems with
fdisk_v2.9n. When trying the verify command, I am always warned that
partitions conflict. This is for any cylinders which cross the 1023
boundary. Looking at the partition table in expert mode shows that
fdisk doesn't report cylinders above 1023. 

Expert command (m for help): p

Disk /dev/sda: 255 heads, 63 sectors, 1115 cylinders

Nr AF  Hd Sec  Cyl  Hd Sec  Cyl   Start    Size ID
 1 80   1   1    0 254  63    2      63   48132 83
 2 00   0   1    3 254  63 1022   4819516386300 83
 3 00   0   1 1023 254  63 102316434495 1220940 83
 4 00 254  63 1023 254  63 102317655435  257040 82


In regular mode the table looks like this

Disk /dev/sda: 255 heads, 63 sectors, 1115 cylinders
Units = cylinders of 16065 * 512 bytes

   Device Boot    Start       End    Blocks   Id  System
/dev/sda1   *         1         3     24066   83  Linux
/dev/sda2             4      1023   8193150   83  Linux
/dev/sda3          1024      1099    610470   83  Linux
/dev/sda4          1100      1115    128520   82  Linux swap


Although fdisk complained of conflicts, I have seen no problems yet
with this Red Hat 6.0 system.

===

Subject: Re: [OT] Mixing SCSI and IDE drives. 
From: Rick Forrester <rickf@crow.jpl.nasa.gov>
Date: Tue, 26 Oct 1999 06:40:23 -0700



mcamacho@habitat.co.cr said:
> Dear friends, I am assembling a new box for myself, and I was adviced
> on the computer shop not to mix IDE and SCSI drives. I have been told,
> too, that I can only get a better performance of an SCSI hard disk
> over an IDE hard disk if I have more than one hard disk. On the other
> hand, I want to burn CD's, so, I've been told that SCSI CD-RW work
> better than IDE ones.

> Now, as I am an "amateur" and you are the "pros" on Computer Science,
> I would  really appreciate your help on the following:

> 1. Can I mix SCSI & IDE disks with "no pain"? 2. Does SCSI CD-RW
> really have a better performance than IDEs? 3. Would it make sense to
> install an SCSI CD-RW and a SCSI CD-R, and use an IDE hard disk?

Hi Manuel,

Well, as is all too often the case, the computer shop doesn't know what
they're talking about, and dispensed bad information.  There may have
been problems with some earlier systems, but not recently.  My last 4
boxes I've built have had a mix of IDE & SCSI devices in them, using
Symbios, BusLogic, & Adaptec controllers without problems.  My primary
system at home is based on an Asus P2B motherboard (be sure to turn off
the SCSI BIOS option in the BIOS when using a card with it's own SCSI
BIOS such as BusLogic or Adaptec).  It's currently using an Adaptec
AHA 2940U2W controller.  The IDE side has an IBM 4.3Gb IDE drive as
/dev/hda, a Toshiba 36X IDE CD_ROM drive, and an LS-120 drive as 
/dev/hdb.
Over on the SCSI side I've got 2 Seagate ST32350W 2.1Gb SCSI drives,
and IBM 18.3Gb U2W SCSI drive, and a Plextor 820 CDR drive.  Everyone
plays well together.

My advice would just be to check the motherboard BIOS options carefully;
some mb's have built in SCSI BIOS, which lets them use cards which don't
have their own SCSI BIOS to support booting, etc.  If your controller
has a built in BIOS, then turn off the SCSI BIOS option in the mb BIOS.
Check the other BIOS options, especially the boot drive options with
care.  Be sure you use decent quality (not necessarily expensive)
cables on the SCSI side, especially, and be sure your SCSI buses are
properly terminated, preferably with active termination in my 
experience,
either by the last device on each chain or with a terminator at the
end of the cable.

===

Subject: Re: [OT] Mixing SCSI and IDE drives.
From: Jim Morris <Jim@Morris.net>
Date: Tue, 26 Oct 1999 08:52:28 -0500


Hello Manuel,

Monday, October 25, 1999, 9:31:03 PM, you wrote:

Camacho> Dear friends, I am assembling a new box for myself, and I was adviced on the
Camacho> computer shop not to mix IDE and SCSI drives. I have been told, too, that I can
Camacho> only get a better performance of an SCSI hard disk over an IDE hard disk if I
Camacho> have more than one hard disk. On the other hand, I want to burn CD's, so, I've
Camacho> been told that SCSI CD-RW work better than IDE ones.

That's hogwash.  I've mixed SCSI and IDE on many systems over the
years.  Both my home PC's use a mix of SCSI and IDE devices.

Camacho> 1. Can I mix SCSI & IDE disks with "no pain"?

The only possible pain could be that your SCSI controller will require
an Interrupt. So if the PC is full of expansion cards, and both IDE
channels are in use (they use IRQ 14 and IRQ 15), the availability of
a free IRQ could be an issue. Note however that most modern PCI 2.1
compliant cards do a pretty decent job of sharing IRQ's between cards.
I've got 4 PC's that use both IDE and SCSI - and a full complement of
expansion cards.  The one I am sitting at right now has 4 PCI cards
(including SCSI), an AGP video card, and 1 ISA cards.

Camacho> 2. Does SCSI CD-RW really have a better performance than IDEs?

The difference is in CPU usage.  IDE interfaces require a lot more
work from the CPU to move the data around.  A typical IDE CD-ROM drive
running full-out can consume possibly 30% of the CPU time on an
average desktop system (well - average of maybe a year ago).  The same
holds true for keeping data going to the CD-RW drive.  So if you are
on IDE for everything, so much CPU time is required to keep the data
moving, that you cannot really use the PC during the process of
burning the disc - otherwise, you may cause a drop out.

The benchmark comparisons I saw when I was buying a CD-RW a year or so
ago showed that a SCSI CD-ROM or CD-RW only consumed about 3% of the
CPU on the same system, due to the greater intelligence of the SCSI
interface. I.e. the SCSI adapter can DMA data directly into the host's
RAM, etc.  Most CD-ROM and CD-RW devices do not support the DMA modes
of EIDE interface, either.

Camacho> 3. Would it make sense to install an SCSI CD-RW and a SCSI CD-R, and use an IDE
Camacho> hard disk?

That's what I have here - good fast IBM Deskstar EIDE hard drives, and SCSI
CD-ROM and CD-RW drives (and one old 2GB SCSI hard disk).  For running
a CD-RW, you don't need anything beyond something like an AdvanSys
SCSI2 or Ultra-SCSI PCI card, which is probably $40-$70.  I've used a
lot of NCR/Symbios chipset based SCSI adapters too.

Camacho> BTW, system is for personal use at home - which means from 10:00 pm to 1~2:00 am
Camacho> =).

Definitely go SCSI for your CD-ROM and CD-RW - but IDE for the hard
drives.  It will let you get a LOT more drive capacity for the $$$'s
than SCSI hard drives will provide.

===

Subject: Re: [OT] Mixing SCSI and IDE drives.
From: Gregory Hosler <gregory.hosler@eno.ericsson.se>
Date: Wed, 27 Oct 1999 08:41:13 +0800 (SGT)



On 26-Oct-99 J. Scott Kasten wrote:
> Well, there are varying issues here.  You can mix SCSI and IDE in a system,
> however
> it can be a chanllenge due to limited resources such as DMA channels and
> interrupts.
> Things like soundcards always hog more than their share, and most PCs today
> come with
> dual IDE controllers on the main board, so there may not be enough left over
> to put
> that SCSI card in.

you don't need to enable both channels if you are not using both channels.
 
> As far as speed, that's a somewhat complicated issue.  Here's the simplest
> rule of
> thumb.  If you consider a single drive on a single controller, then a modern
> IDE
> drive on a modern IDE interface with the more advanced transfer modes turned
> on
> will be faster than the mid generation SCSI drives (AKA Fast SCSI, SCSI II)
> in
> terms of bus transfer.  However the high end WIDE and ULTRA WIDE SCSI (read
> EXPEN$IVE)

relatively speaking, your WIDE /UW / LVD scsi will be more expensive than
"mid range" scsi, and either will be more expensive than IDE. But the cost
increment, these days, is not that great (compared to, for example, the
cost increment several to 5 years ago, when scsi was about us$1k per gb)

===


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