Re: 2Gb Exp problems 8.1.7

Billy Verreynne wrote:

> Frank wrote:
>
> > Could some OS guru elaborate on why some OS's only handle 2GB?
> > Seems to me these must be 31 bit then. (AIX 4.x had a special
> > 'add-on' to go beyond 2GB, looked like the MSB was enabled, so to speak)
>
> Won't call myself an OS guru, but I will have a bash (don't like ksh or csh
> that much ;-).
>
> Firstly, it has _nothing_ to do with operating system and _everything_ to do
> with the file system.
>
> And this type of problem has been around for a long while. Back in my
> mainframe days, the filesystem used on the Siemens BS2000 o/s (still IMO
> one of the best mainframe o/s's ever) used a single byte for storing extent
> number. Thus you were limited to 255 extents. (wasn't this also the case
> with Oracle extents a few versions ago?)
>
> Using DOS old FAT16 filesystem is no different. The File Allocation Table
> has also size restrictions. Thus, a completed path of a subdirectory can
> only be (if I recall correctly) also 255-256 characters in total. When you
> reached that limit, you can not create any more subdirectories.
>
> Okay, now for ionodes and Unix. A file is represented by a structure called
> an inode (similar to a FAT entry).
>
> Each inode contains stuff like file type, access rights, timestamps, size,
> pointers to data blocks, and so on. A bunch of data blocks make up a file.
> Their addresses are stored in that file's inode.
>
> An ionode is of a certain size. Thus, you are limited to the number of data
> block pointers (or addresses) you can store in the ionode of a file.
>
> Here are a table listing Unix filesystems used by Linux through the years:
> Minix ext ext2
> Max fileystem size 64MB 2GB 4TB
> Max file size 64MB 2GB 2GB
>
> Because operating systems are closely tied to specific filesystems (often
> only running on a single specific filesystem), filesystem limitation such
> as the 2GB filesize limit is seen as an operating system issue. Which is
> not really the case as that limitation belongs solely to the filesystem.
>
> --
> Billy

You are correct but I don't see the separation as clearly as you do. If an O/S doesn't support a file system it is the O/S that is the issue.

In the case of some O/Ss they default to 2GB files and default parameters in the O/S can be changed to allow larger files. The makes it look, again, like the O/S to me.

Daniel Morgan Received on Fri Feb 14 2003 - 03:15:00 CST