Subject: Re: Questions: swapping and panics, disk speed
To: David Crooke <firstname.lastname@example.org>
From: Michael L. Hitch <email@example.com>
Date: 03/26/1995 10:56:37
On Mar 25, 10:29pm, David Crooke wrote:
> Quantum LPS 49Mb HDD, SCSI id 2, 1 partition = AmigaOS 49Mb
> Maxtor 7345S 330Mb HDD, SCSI id 6, 5 partitions =
> AmigaOS 50Mb, NetBSD swap 32Mb, NetBSD /local 120Mb, NetBSD /usr 100Mb,
> NetBSD root 20Mb
> Wangtek 5150ES tape, SCSI id 4 (external)
> 1. I am mounting the swap partition from /etc/fstab as /tmp - is this
The swap partition can't be mounted - it's configured into the kernel
from the config file.
The /etc/fstab entry for /tmp is mounting a virtual memory file system.
The special device (i.e. the swap partition) is used for the parameters
of the memory file system, and I think it specifies the device to use
for paging the virtual memory.
> 2. Using "df /tmp" it only reports the amount of space used by /tmp
> files, the rest is marked as free, irrespective of the amount of
> (virtual) memory in use. Is this normal? What happens if it fills up
> with files and there's no swap space?
I think that is normal behaviour. The default parameters to the
memory file system will allow that file system to use up all the swap
space, so you could easily run out of swap space. To prevent that, you
need to restrict the size of the memory file system with the -s option.
> 3. The kernel seems over enthusiastic about swapping out to disk.
I don't know much about this one.
> 4. Disk access is very slow (not a NetBSD problem). I am making a new
> SCSI cable for the internal bus and will shuffle the drive order. Will
> that help? I have seen close to 2Mb/sec sustained from most of the
> drives but the best on offer is around 500K/sec with the current setup
> (correctly terminated). Comments?
The 7345S drive is not particularly fast. I bought a 7345S and a 540M
Fast SCSI-2 drive, and the 540M drive performs much, much better. I am
able to get 2Mb/sec sustained on the first part of the 7345S using 64K
blocks, and 1.6Mb sustained for the whole disk. This is on my Zeus Fast
SCSI-2 controller (the drive runs with fast sync mode - 100ns period).
I don't think the A3000 driver in 1.0 uses sync mode by default, but I
wouldn't expect that to slow down the transfer rate that much. I think
seek speed is more critical here than the raw transfer rate.
What test are you using to get the transfer rates? I use dd on the
character device and use 64K blocksize for the best rate.
> 5. On startup, NetBSD reports the Quantum as SCSI2 and the Maxtor as
> SCSI1 - I am sure the reverse is true. Is this a known "minor
> feature"? For what it's worth I think it says the tape drive is SCSI1
> but I've personally no idea what it should be.
Nope, the 7345S is only a SCSI1 drive, although it does appear to
support Fast synchronous transfers. I don't know anything about the
The Wangtek tape drive is only SCSI1.
> 6. What do I need to do to make stuff binary-compatible with a Sun3
> 68020 running SunOS 4.0 ? A method to get static link binaries (no
> ld.so) would do.
Assuming that you mean how to create a binary on NetBSD that can run
on the Sun3, you would need to write a SunOS version of the C startup
code, and SunOS versions of all the system calls. Any other library
routines that might have SunOS dependancies would be needed. You might
also need a modified ln to create the Sun3 executable, unless the NetBSD
version has a way to specify a different binary format.
Michael L. Hitch INTERNET: firstname.lastname@example.org
Office of Systems and Computing Services
Montana State University Bozeman, MT USA