IDE Zip disk faster via ide-scsi ???

IDE Zip disk faster via ide-scsi ???

Post by Igor Boukan » Sat, 10 Jun 2000 04:00:00



When I enabled SCSI interface emulation to my 100 MB IDE Zip drive
(via modprobe ide-scsi) I noticed significant performance improvements,
i.e. "dd if=/dev/zip of=/dev/null" started to run 20% faster with
zip=/dev/sda4 than it had been with zip=/dev/hdd4.  

Are there any reasons for that? I mean if you so easily can improve
performance by 20% with this trick why it is not on by default???

Regards, Igor

 
 
 

IDE Zip disk faster via ide-scsi ???

Post by Andrey Vlaso » Sat, 10 Jun 2000 04:00:00


Hi Igor,

I remember that I read one day that ZIP drive inside is SCSI.
If it true - it a reason why it faster in SCSI emulation mode.

Andrey


> When I enabled SCSI interface emulation to my 100 MB IDE Zip drive
> (via modprobe ide-scsi) I noticed significant performance improvements,
> i.e. "dd if=/dev/zip of=/dev/null" started to run 20% faster with
> zip=/dev/sda4 than it had been with zip=/dev/hdd4.

> Are there any reasons for that? I mean if you so easily can improve
> performance by 20% with this trick why it is not on by default???

> Regards, Igor


 
 
 

IDE Zip disk faster via ide-scsi ???

Post by Duan » Sat, 10 Jun 2000 04:00:00



> When I enabled SCSI interface emulation to my 100 MB IDE Zip drive
> (via modprobe ide-scsi) I noticed significant performance improvements,
> i.e. "dd if=/dev/zip of=/dev/null" started to run 20% faster with
> zip=/dev/sda4 than it had been with zip=/dev/hdd4.

> Are there any reasons for that? I mean if you so easily can improve
> performance by 20% with this trick why it is not on by default???

> Regards, Igor

dd speed is very dependent on block size. Try again without ide-scsi,
but use:
 dd if=/dev/zip of=/dev/null bs=65536

That will probably also speed things up. Pure guesswork ahead -> Perhaps
the ide-scsi driver uses a different default blocksize from the standard
ide driver.

In general, dd is not a good way to measure performance. I also cannot
really think of a reason why you would want to use it. Linux will do the
same thing using the device file as an argument to "cp". Try this and
compare to the speed of dd:
cp /dev/zip /dev/null

And no, that is not copying the "files" from the zip drive, but is doing
a byte by byte raw device copy, just like dd. That is because /dev/zip
is a raw device, not a filesystem.

This is very handy in these days of large cheap disks. Buy an identical
copy of your root disk, plug it in, boot single user mode, and do "cp
/dev/hda /dev/hdb". It will copy boot partitions, windoze partitions,
Linux partitions, and everything. Stick it on a shelf for the day when
your disk crashes - it is always handy to have a spare disk around
anyway. On my system with 32 bit UDMA33 disk accesses enabled, it took
35 minutes to copy a 20 GB disk.

--

 
 
 

IDE Zip disk faster via ide-scsi ???

Post by Richard Townsen » Sun, 11 Jun 2000 04:00:00


On a related topic, I bought an IDE (ATAPI) Zip 250 drive (internal) last
year, and I've never been able to get it working properly as an ATAPI
Floppy drive. It seems that the drive reports two different capacities to
the kernel, the kernel then gets confused, and writing data to the drive
hangs after a certain amount of activity (and the data get corrupted).

I posted a few messages to this NG back then, to see if anyone had any
idea what was happening - no joy. So, in the meantime, I've been using
SCSI emulation. Has anyone else had this problem? And does anyone know of
a fix?

cheers

Rich


> Hi Igor,

> I remember that I read one day that ZIP drive inside is SCSI.
> If it true - it a reason why it faster in SCSI emulation mode.

> Andrey


> > When I enabled SCSI interface emulation to my 100 MB IDE Zip drive
> > (via modprobe ide-scsi) I noticed significant performance improvements,
> > i.e. "dd if=/dev/zip of=/dev/null" started to run 20% faster with
> > zip=/dev/sda4 than it had been with zip=/dev/hdd4.

> > Are there any reasons for that? I mean if you so easily can improve
> > performance by 20% with this trick why it is not on by default???

> > Regards, Igor

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IDE Zip disk faster via ide-scsi ???

Post by Christopher McCla » Wed, 14 Jun 2000 04:00:00



> When I enabled SCSI interface emulation to my 100 MB IDE Zip drive
> (via modprobe ide-scsi) I noticed significant performance improvements,
> i.e. "dd if=/dev/zip of=/dev/null" started to run 20% faster with
> zip=/dev/sda4 than it had been with zip=/dev/hdd4.

> Are there any reasons for that? I mean if you so easily can improve
> performance by 20% with this trick why it is not on by default???

> Regards, Igor

Hi...

Could you please enlighten me as to where I might find out how to use
ide-scsi for an IDE zip drive. Presumably then all the normal zip drive
tools will work with the drive and I can eject it properly as well
etc...

Cheers

Cim

 
 
 

IDE Zip disk faster via ide-scsi ???

Post by Igor Boukan » Thu, 15 Jun 2000 04:00:00



Quote:> Hi...

> Could you please enlighten me as to where I might find out how to use
> ide-scsi for an IDE zip drive. Presumably then all the normal zip drive
> tools will work with the drive and I can eject it properly as well
> etc...

> Cheers

> Cim

Well, that was a unexpected consequence that my friend discovered
by mistake.

First you have to tell kernel not to use ide driver for your zip.
You can do it via
        append="hdd=ide-scsi"
in /etc/lilo.conf for your kernel image. According to CD-Writing-HOWTO
it works at least witn 2.0 kernels starting with 2.0.37 and with 2.2
starting with 2.2.10. Here is my lilo.conf were I assigned ide-scsi
to handle CD-ROM (/dev/hdc) as well:
------------/etc/lilo.conf---------------------------------
boot=/dev/hda
map=/boot/map
install=/boot/boot.b
prompt
timeout=50
linear
#default=linux
default=linux-ide-scsi

image=/boot/vmlinuz-2.2.14-5.0
        label=linux
        read-only
        root=/dev/hda2

image=/boot/vmlinuz-2.2.14-5.0
        label=linux-ide-scsi
        read-only
        root=/dev/hda2
        append="hdc=ide-scsi hdd=ide-scsi"
------------------------------------------------------------------

Then you have to call somehow "modprobe ide-scsi" during boot.
For that I just created the following /etc/rc.d/rc.modules:

-------------------/etc/rc.d/rc.modules----------------------
#!/bin/sh
/sbin/modprobe ide-scsi
------------------------------------------------------------

RedHat 6.* is calling this file from /etc/rc.sysinit

Before this change I had for "dd if=/dev/zip of=/dev/null bs=65536"
running time on average 1m55s for 100 MB zip drive, and never better
then 1m50s, but after that it became 1m33s with best result 1m31s.
So it helped. Another advantage is that I can use readcd command to
try to read corrupted zip drive and not only scratched music CD.

And "eject /mnt/zip" does work now.

Regards, Igor

 
 
 

1. ide-scsi - How ignore IDE Zip drive?

I have an IDE CDRW and am using the ide-scsi kernel module so that the
cdrecord command can access the CDRW (using the SCSI interface) and
"burn" CD's.  This works well.  However,  the ide-scsi module also grabs
my IDE zip drive.  I do not want this because the SCSI translation
provided by the ide-scsi module does not support the eject function.  Is
there a way to get the ide-scsi module to ignore my IDE zip drive short
of changing the source code and recompiling?

I am using RedHat 6.1 (Intel)
Linux kernel version 2.2.12

Any help is appreciated.

--
Ken Pratt

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