Iomega ZIP100 SCSI quite slow

Iomega ZIP100 SCSI quite slow

Post by Harald Hanche-Olse » Mon, 20 Nov 2000 09:09:12




| are there any special configuration issues concerning Iomega ZIP100
| drives? Mine is working fine with Windows and Linux; FreeBSD correctly
| recognizes it at startup, but all read/write operations are extremely
| slow. Usually, when copying 30 MBytes to a ZIP medium, it takes about 45
| seconds, but with FreeBSD, this operation takes almost 6 minutes.
| The two cd-rom devices that are connected to the same SCSI controller
| (Adaptec 2940AU) work fine and as fast as the should do, and the whole
| rest of the system seems well-configured.

I too find the zip drive annoyingly slow if I use zip disks with msdos
file systems.  Put a ufs file system on it, however, and you should
find things speeding up quite nicely.  This may not be an option if
you are using the zip to transfer data to and from dos/windoze
systems, but if your zip disks live in a pure freebsd world it't
definitely the way to go.

If I needed regularly to transfer largeish amounts of data onto and
off from a zip disk, I'd probably experiment with keeping an msdos
file system in a regular file on a hard drive, then transferring whole
disk images to and from the zip using dd.

--
* Harald Hanche-Olsen     <URL:http://www.math.ntnu.no/~hanche/>
- Yes it works in practice - but does it work in theory?

 
 
 

Iomega ZIP100 SCSI quite slow

Post by Harald Hanche-Olse » Mon, 20 Nov 2000 04:00:00




| > I too find the zip drive annoyingly slow if I use zip disks with
| > msdos file systems.
|[...]
| I wonder why this problem exists, as a zip medium seems to be the
| same as a hard drive partition (to the os), and the Windows hard
| drive partitions I work with seem to work without any problems.

I really couldn't say, but I can always speculate.  And my speculation
says that zip disks have long seek times, and maybe there is something
either about msdos file systems or about the way it's implemented
under freebsd that leads to a lot of seeking (from file to directory
and back), which then kills performance.

| Is there any known fix/workaround for this problem except keeping an
| image on the hard disk and then dding it to the medium? It might
| even be faster than usual file transfers to the zip disks,
| especially if you have many small files, but the direct way is just
| a bit more comfortable.

Indeed.  Sorry, I don't know any other workaround, nor do I know for
sure if the one I suggested will work.
--
* Harald Hanche-Olsen     <URL:http://www.math.ntnu.no/~hanche/>
- Yes it works in practice - but does it work in theory?

 
 
 

Iomega ZIP100 SCSI quite slow

Post by Doug Perha » Tue, 21 Nov 2000 04:00:00



> Hi everyone,

> are there any special configuration issues concerning Iomega ZIP100
> drives? Mine is working fine with Windows and Linux; FreeBSD correctly
> recognizes it at startup, but all read/write operations are extremely
> slow. Usually, when copying 30 MBytes to a ZIP medium, it takes about 45
> seconds, but with FreeBSD, this operation takes almost 6 minutes.

Let me preface this by saying I do not have a zip disk, nor am i an
expert. However, when the issue of "disk fast on linux, slow on FreeBSD"
comes up, some smart guy usually brings up the notion of mounting the
drive as "async" or "soft updates" rather than in "sync" mode.  Linux
from what I hear mounts disks in "async" mode by default, while FreeBSD
mounts "sync" mode by default.  No flames please, I barely know what I'm
talking about.  Perhaps some "smart guy" can set the details straight.

Quote:> The two cd-rom devices that are connected to the same SCSI controller
> (Adaptec 2940AU) work fine and as fast as the should do, and the whole
> rest of the system seems well-configured.
> Thanks for any hints.

> Regards,
> SW
> --
> When all other means of communication fail, try words.
> http://transfer.to/dunkelkammer

> GPG fingerprint: AB98 8346 C2C9 A47E 86E4  D603 84DE 0532 31FA 114C

--
Doug Perham                                          o{..}o    

WorldGate Communications, Inc.                        (______)\
                                                      / \  / \  
 
 
 

Iomega ZIP100 SCSI quite slow

Post by D. Roc » Tue, 21 Nov 2000 04:00:00



> Hi everyone,
> are there any special configuration issues concerning Iomega ZIP100
> drives? Mine is working fine with Windows and Linux; FreeBSD correctly
> recognizes it at startup, but all read/write operations are extremely
> slow. Usually, when copying 30 MBytes to a ZIP medium, it takes about 45
> seconds, but with FreeBSD, this operation takes almost 6 minutes.
> The two cd-rom devices that are connected to the same SCSI controller
> (Adaptec 2940AU) work fine and as fast as the should do, and the whole
> rest of the system seems well-configured.
> Thanks for any hints.

SCSI ZIPs (don't know about IDE - don't have one) can only perform a limited
number of commands per second (~ 40 IO-ops/s max).

The FreeBSD msdosfs filesystem cannot do clustered reads or writes - it uses
one IO-op per cluster (usually 2 kB for 100MB ZIPs). So you end up with
80 kB/s.

If you need FAT, install mtools to access the ZIP drive. mtools to cluster
reads and writes and you should get near 600-900 kB/s.

--
Daniel

 
 
 

Iomega ZIP100 SCSI quite slow

Post by Harald Hanche-Olse » Wed, 22 Nov 2000 09:03:27



| I tried to read an image of the disk with dd ten minutes ago. I aborted it
| after some minutes; dd said the throughput was 25024 bytes/sec. Looks
| like it isn't the filesystem, in the end.

Hmmm...  As D. Rock says elsewhere in this thread, there is a problem
with the number of operations per second on the SCSI zip disk, so do
as he says and use mtools.

  This simple experiment highlights the problem (my zip is on da0c):

#; dd if\=/dev/da0c of\=/dev/null bs\=10240 count\=1000
1000+0 records in
1000+0 records out
10240000 bytes transferred in 26.577852 secs (385283 bytes/sec)

#; dd if\=/dev/da0c of\=/dev/null bs\=1024 count\=10000
10000+0 records in
10000+0 records out
10240000 bytes transferred in 206.129291 secs (49678 bytes/sec)

--
* Harald Hanche-Olsen     <URL:http://www.math.ntnu.no/~hanche/>
- Yes it works in practice - but does it work in theory?

 
 
 

Iomega ZIP100 SCSI quite slow

Post by D. Roc » Wed, 22 Nov 2000 09:37:00




>> If you need FAT, install mtools to access the ZIP drive. mtools to cluster
>> reads and writes and you should get near 600-900 kB/s.
> Thanks for the reply, but as you can read in my other posting in this
> thread, this doesn't seem to be a filesystem problem, but something to do
> with SCSI.

...and mtools are (for FAT) the solution - even for the SCSI problem.
mtools to clustered reads/writes and speed up I/O performance on ZIP drives
significantly (instead of using 2k blocks they write in much larger
chunks, reducing the overhead per I/O-command).

--
Daniel

 
 
 

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