(((We are a multi-user facility with a Bio-Rad MRC-1000.  We
have
Panasonic 1 gigabyte read/write/erasable optical disks as our
mass storage
medium.  One of our users has had a persistent problem which
was unique but
happened to every new disk we gave her lab within a 2-3 week
period.  After
tearing our hair out, working with Bio-Rad technical support
and service
person, a casual conversation with a computer expert solved
the problem.  It
seems that this user was collecting single optical slice files
(relatively
small number of bytes) therefore she was able to accumulate
300, 500 or similar
ranges on each side of the disk.  Evidently, there is some
limit to the ability
of the root directory to store a given number of files. My
computer expert
recommended that several subdirectories be made, and those do
not suffer from
the same problem.  We then limit the number of files in the
root directory to
about 100, set up subdirectories that can have several hundred
files, and then
the problem disappears.  The user can now write to her disk
all the time, and
no files have been scrambled.  I am not sure if this applies
to all optical
disks, but if anyone out there has had problems where disks
containing several
hundred files can be read but not written to, this may be your
solution.
 
        Dr. Andrea Elberger
        Professor, Anatomy and Neurobiology
        The University of Tennessee, Memphis
        [log in to unmask])))
 
I am replying to Dr. Elberger's e-mail. The problem outlined
is nothing really to do with the optical disks or Panasonic,
but rather a quirk of Microsoft DOS. Even the latest Ver6.22
of DOS only allows a maximum of 512 files in the root
directory of any logical unit. The workaround described is the
correct solution, namely to have lots of subdirectories, which
can have unlimited numbers of files in each subdirectory.
 
Bill Mason
Lab of Neural and Secretory Signalling
Babraham Institute
Babraham, Cambridge   CB2  4AT
United Kingdom
E-mail: MASONW @ BBSRC.AC.UK