As Andrew Reilly wrote:

> Can anyone comment on whether the Fujitsu DynaMO
> magneto-optical 640M drives work with FreeBSD or NetBSD?

FreeBSD even has an own driver handling the slightly different
requirements of removable media devices (od(4)).  If this drive probes
as T_OPTICAL (type 7), it should be automatically assigned to the
od(4) driver.

The plain sd(4) driver should work as well, but things like ignoring
the first unit attention condition after a media change, or handling
the insertion of a medium with a different size might fail, or at
least cause annoying warnings.

> There seems to be several varieties of media available, but
> the types my local dealer has are the 230M and 640M.  From a
> quick study of the Fujitsu web site, the 128M, 230M and 540M
> formats have 512-byte sectors, so I would not expect any
> problems with these.

I would expect the same.

> The 640M capacity disks have 2k-byte sectors, though.  I
> know that most BSD filesystems make some pretty strong
> assumptions about the size of sectors, but wondered whether
> there were work-arounds in place.

The filesystems don't make many assumptions about the sector size, but
the filesystem implementations do.  FreeBSD tries to handle some of
the issues of sector sizes > 512 bytes, but i know it's not yet at the
point where it should be.  So it might work, but it might also fail.

> I guess I could put a TAR archive on one of these even if an
> FFS partition does not work?

Sure, you can always use the raw device, with the appropriate block
size.  For a 2 KB medium, you should be able to create an ISO9660
filesystem and mount it without problems. :-)

-- 
cheers, J"org

joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)