Re: File Limits

[Paul Crawford <psc@sat.dundee.ac.uk>]

Dear Xavier,
> So here's my problem: Until now I was using dosemu with ms-dos 6.22 to run an old database. A little while ago we had some big changes to the tables and they grew a lot.
> Yesterday I realized that we have a database file that is about to hit 2 Gb. I remembered that some time ago, we hit a bug on our program and it endlessly inserted rows on a table until it hit the 2 gb mark. Then the file either disappeared or became a 0 bytes file, I don't remember well.
> So I started reading and found that ms-dos 6.22 only supports FAT16 and apparently it only allows 2 gb volumes, and 2 gb files.
> So I thought of using ms-dos 7.10 which supports fat32 and would give us 4 gb files. But the same happens. The files disappear as soon as they hit the 2 gb mark. And when I execute the dir command, it always reports 2 gb of free disk space, which is odd.
>
> I don't know if this is a limitation of dosemu or I'm doing something wrong. Right now, I have about 140 users. On each $HOME/.dosemu/drive_c/ of the users there are symlinks to each file in /usr/share/dosemu/drive_z/ , where ms-dos is located. And I have the database files in /datos/ . I use lredir to make it appear as f: to every user.
> All of this is in the same ext3 partition.
>
> Any ideas?

The standard limits for 32-bit Linux programs is 2GB per file, even 
though ext3 allows much, much more total space (and file size).

Have you tried using a 64-bit Linux and matching dosemu version?

I know it is not always as successful (e.g. I found the Microsoft C6 
compiler works fine on Ubuntu 10.04 32-bit, but crashes/closes dosemu on 
64-bit on the same hardware) but that would be my first suggestion to try.

Failing that, you may have to consider modifying the application to 
split your data set or to store pointers to other data sets, etc, all of 
which is a whole lot more trouble than just running it under dosemu!

Regards,
Paul
-- 
  Dr. Paul S. Crawford
  c/o Satellite Station
  University of Dundee
  Small's Wynd, Dundee, DD1 4HN
  Email: psc@sat.dundee.ac.uk
  Tel: +44 (0)1382 38 4687
  The University of Dundee is a Scottish Registered Charity, No. SC015096