Return to 1.2_caveats.html CVS log

Up to [Development] / xfs-website.orig

 Added Files:
 	1.2_caveats.html

<& xfsTemplate,top=>1,side=>1 &>

<!-- Start Project Content -->
<h2>
<b><font face="ARIAL NARROW,HELVETICA">XFS for Linux Release 1.2 Caveats</font></b></h2>

<p>
You must take the following issues into account
when you create and administer
XFS filesystems with XFS for Linux Release 1.2.
</p>

<h3>Size and Memory Limitations</h3>

<ul>
<li>
2 Terabyte filesystem limitation
</li>

<p>
Currently XFS is limited to filesystems smaller that 2 terabytes.
This is due to limitations in the Linux block device I/O layers.
</p>

<p>
The XFS team is working with Linux developers to improve the Linux
I/O layers. The improvements will include the support necessary to 
exceed 2 Tbyte filesystems.
</p>
</ul>

<h3>Compiler and Library Releases</h3>

<ul>
<li>
Unsupported compiler releases
</li>


<p>
The following compiler versions are not supported under
XFS:
<ul>
<p>
<li>gcc version 2.95.1
<li>gcc version 2.95.2
<li>gcc version 2.95.3
<li>RedHat 2.96-100 and earlier
</ul>
<p>
The easiest way to check what version is in
use is by running <tt>gcc -v</tt>.
</p>


<li>
glibc version 2.1.3 or later required
</li>

</ul>

<h3>Userspace Tools Release 2.0.0 or Later Required </h3>

<ul>
<p>
XFS userspace tools release 2.0.0 or later are required
for this release of XFS Linux.
Instructions for creating the XFS tools are provided
<A href="kernelconf.html"> Configuring and Installing the
XFS Linux Kernel</A>.
</p>
</ul>

<h3>
Using Kernel 2.4.18 as an NFS Client with IRIX Server
</h3>

<ul>
<p>
EOVERFLOW errors may result when using 2.4.18 as an NFS client and
an IRIX server with version 1 directories.
</p>

<p>
Applying patch
<A HREF="http://www.fys.uio.no/~trondmy/src/2.4.13/linux-2.4.13-seekdir.dif">
http://www.fys.uio.no/~trondmy/src/2.4.13/linux-2.4.13-seekdir.dif</A>.
to 2.4.14 and exporting the version 1 directory on IRIX with the "32bitclients"
option alleviates this problem.
</p>
</ul>

<h3>XFS Features</h3>

<ul>
<li>
New system calls
</li>

<p>
The official system calls for extended attributes are used in
this release.  These are getxattr(2), listxattr(2), removexattr(2)
and setxattr(2).  Extended attributes can be manipulated using the
getfattr(1) and setfattr(1) commands.
</p>

<p>
Library calls implement all of the draft Posix 1003.1e standard
functions, such as: acl_copy_ext(3), acl_delete_def_file(3),
acl_dup(3), acl_free(3), acl_from_text(3), acl_get_fd(3),
acl_get_file(3), acl_set_fd(3), acl_set_file(3), acl_size(3),
acl_valid(3).  Access control lists can be manipulated using the
getfacl(1) and setfacl(1) commands.  See the associated man pages
for details.
</p>

<li>
Quotas 
</li>

<p>
User quotas and group quotas are now functional.
</p>

<li>
Migrating from non-XFS to XFS 
</li>

<p>
The Linux version of dump and restore can be used to migrate 
data from a non-XFS volume to an XFS volume.
Linux dump, however, cannot be used to dump an XFS volume as it uses
ext2 library functions.
</p>

<li>
Migrating from IRIX XFS to Linux XFS 
</li>

<p>
xfsdump and xfsrestore can be used to migrate an IRIX XFS volume
to a Linux XFS volume and vice versa.
</p>

<li>
Backup and restore
</li>

<p>
xfsdump and xfsrestore should be used for backup and restore
of XFS volumes.
</p>

<li>
DMAPI-managed filesytem backup and restore
</li>

<p>
xfsdump and restore may be used to move DMAPI-managed filesystems between IRIX
and Linux.  The HSM that uses that DMAPI filesystem must also
support the moving of the filesystem between big- and little-endian machines.
</p>
</ul>

<h3>XFS Caveats and Limitations</h3>

<ul>

<li>
LVM unsupported on IA-64 architecture
</li>
<p>
The LVM volume manager is not currently supported for IA-64
architecture.  We recommend using md for IA-64.
</p>



<li>
XFS version 2 directory format
</li>

<p>
IRIX XFS supports two directory formats, referred to as
version 1 and version 2.  Linux XFS supports version 2 only.
XFS filesystems that need to be migrated from IRIX to Linux
systems must use the version 2 directory structure.
</p>

<p>
The mkfs command creates version 2 directory format
filesystems by default in IRIX release 6.5.14 and
later.  You can determine what directory format version
exists on an IRIX filesystem with the following command:

<pre><tt>
xfs_growfs -n mount-point | grep naming
</tt></pre>
</p>

<p>
For example:

<pre>
# <tt><B>xfs_growfs -n / | grep naming</B>
naming   =version 1              bsize=4096  
</tt></pre>
</p>

<li>
Filesystem block size limitation
</li>

<p>
The maximum filesystem block size is the page size of
the kernel.  
On a x86 architecture that size is 4 Kbytes.
On IA-64 architecture, the page size is set at compile time.
</p>

<p>
Note that filessystems created on an IRIX/MIPS platform must have been 
created with a 4 Kbyte or less block size in order to be mounted on
a ia32 Linux system.
</p>

<li>
Unwritten extents unsupported
</li>

<p>
The unwritten extent feature is not yet operational.
Currently this is the default setting for mkfs.xfs on Linux.
</p>

<li>
Realtime volumes not implemented
</li>

<p>
Realtime volumes are not yet tested in XFS Linux and should not be
used.
</p>


<li>
Changing filesystem permissions
</li>
<p>
It is possible to remount an XFS filesystem to change its permissions
from read/write to read-only.  This support is needed for
XFS to function as a root filesystem.
</p>

<li>
Software RAID5 performance
</li>
<p>
XFS 1.2 supports MD RAID0, RAID1 and RAID5. RAID5 with an internal log
may perform slightly worse with XFS than with ext2. This will be
addressed in a future release.
</p>


<li>
The fsr utility and system partitions
</li>

<p>
In general we do not foresee the need to run fsr on system partitions
such as /, /boot and /usr as these will in general not suffer from
fragmentation. There are also issues with defragmenting the files
lilo uses to boot your system.  Should these files be moved by fsr
then you must rerun lilo before you reboot or you may
have an unbootable system.
</p>

</ul>



<h3>Issues with Red Hat 7.x</h3>

<ul>
<li>
Compiler versions
</li>

<p>
Red Hat Linux ships with 2 compilers, "gcc" and "kgcc."  kgcc is essentially an
older gcc (egcs-2.91.66) which should be used to compile the kernel.
To use this compiler, comment out the following line in the top level kernel
makefile:

<pre><tt>CC              = $(CROSS_COMPILE)gcc -V egcs-2.91.66</tt></pre>

And uncomment the following line:

<pre><tt>CC              = $(CROSS_COMPILE)kgcc</tt></pre>
</p>

<p>
kgcc is available in the "compat-egcs" package on Red Hat Linux 7.1 and
7.2.
</p>
</ul>


<br>


<& xfsTemplate,bottom=>1 &>