From: | byron(at)cc(dot)gatech(dot)edu (Byron A Jeff) |
---|---|
To: | pgsql-hackers(at)postgresql(dot)org, pgsql-admin(at)postgresql(dot)org, pgsql-general(at)postgresql(dot)org |
Subject: | Re: Largest filesize under Linux |
Date: | 2003-03-11 18:41:31 |
Message-ID: | b4lakr$pd3@cleon.cc.gatech.edu |
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Lists: | pgsql-admin pgsql-general pgsql-hackers |
In article <e4pba(dot)794$yy2(dot)89177201(at)newssvr13(dot)news(dot)prodigy(dot)com>,
Partho Bhowmick <pbhowmick(at)sbcglobal(dot)net> wrote:
-I am working on extending the functionality of PostgreSQL on Linux.
-I need to know what's the largest filesize for a single file that I can have
-under Linux?
The answer is definitive: it depends...
There are multiple layers that have file size restrictions (from bottom to top):
* The filesystem itself on the disk.
* The Virtual File System implementation in the kernel.
* The filesystem library interface.
* The application.
The max file size is the minimum of the allowable file sizes for each
component. Generally there are two available sizes:
* 2.1GB imposed by a +/- 31 bit file offset. Until recently the VFS, library,
and applications imposed this limit.
* 9 million TB imposed by a +/- 63 bit file offset. Most recent distributions
have all 4 elements implementing this filesize.
Here's a simple test. On a filesystem with more than 5GB available try the
following:
# dd if=/dev/zero of=testfilesize bs=1024K count=3000
This will attempt to create a 3GB file which exceeds the 2.1GB max imposed by
31 bit offsets. If the file creation is successful, you can pretty much
create a file of any size.
BAJ
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