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Managing Large Files on VxFS

Managing Large Files on VxFS

The kernel supports the Large File Summit (LFS) API, a standard for large file support that allows the use of files larger than 2GB on 32-bit systems. LFS enables the kernel to support files as large as 1 terabyte (1TB, or 2^40 bytes). A sparse file can exhibit lengths up to 2^63 bytes.

Large file support is available on VxFS filesystems only. By default, the root filesystem is a VxFS filesystem with large files enabled. To check on the status of this support for a filesystem, use the fsadm(ADM) command, as in this example for the root filesystem:

   fsadm /

To create a large file aware filesystem, use the -o largefiles option to the mkfs(ADM) command, and specify a blockize of 8192; as in this eaxmple:

   mkfs -f vxfs -o largefiles,bsize=8192 /dev/rdsk/c0b0t0d0s4

To add large file support to an existing VxFS file system, use fsadm, as in this eaxmple:

   fsadm -f vxfs -o largefiles /myfilesystem

Note that large file support is intended for specialized applications, such as databases. It is not intended for general purpose text files.

For this reason, only a limited set of utilities have been made capable of handle large files (sometimes referred to as being large file aware). Most of these commands are located in /u95/bin, for compatibility reasons: that is, the default versions of these commands (located in /bin, /usr/bin, etc.) must remain the default versions so that legacy applications from earlier releases continue to work properly.

To access the large file aware commands, we recommend that you do not change your PATH variable, but instead use the full pathname of the large file aware commands instead.

The following set of system utilities are large file aware. With the exception of ftp and scp, these large file aware commands are located in /u95/bin.

cat(1)
chgrp(1)
chmod(1)
chown(1)
cksum(1)
cmp(1)
compress(1)
cp(1)
cpio(1)
dd(1M)
df(1M)
du(1M)
ff(1M)
find(1)
fsck(1M)
fsdb(1M)
ftp(1)
ln(1)
ls(1)
mkdir(1)
mkfs(1M)
mv(1)
ncheck(1M)
pathchk(1)
pax(1)
pwd(1)
rcp(1tcp)
rm(1)
rmdir(1)
scp(1)
sum(1)
touch(1)
ulimit(1)
uncompress(1)
zcat(1)

The most notable omissions from the above list are the various Bourne and Korn shells (/bin/sh, /bin/ksh, /u95/bin/sh, /u95/bin/ksh), which are not large file aware. When running one of these shells, shell redirection cannot be used to create or append to files larger than 2GB.

The bash and zsh shells, however, are capable of manipulating files larger than 2GB via shell redirection.

Note that any process that handles large files needs to set the process file size limit using the ulimit command, as follows:

   ulimit -f unlimited

© 2007 The SCO Group, Inc. All rights reserved.
SCO OpenServer Release 6.0.0 -- 05 June 2007