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Update some docs to reflect current XFS capabilities.

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<h1><b><font face="ARIAL NARROW,HELVETICA">
XFS: A high-performance journaling filesystem
</font></b></h1>

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<p>
XFS combines advanced journaling technology with full 64-bit addressing and
scalable structures and algorithms.  This combination delivers the most
scalable and high-performance filesystem in the world.
</p>

<h2><font face="ARIAL NARROW,HELVETICA">
Questions and Problems
</font></h2>
<p>
If you have any questions or problems with the installation or
administration of XFS for Linux, you can send email to 
<a href="mailto:linux-xfs@oss.sgi.com">linux-xfs@oss.sgi.com</a>.
  Note that this address is a public mailing list; please search the 
<A HREF="http://oss.sgi.com/archives/linux-xfs">list archive</A>
to see if your question has been answered previously.
</p>

<p>
To report any bugs you encounter in XFS for Linux, use the
<a href="http://oss.sgi.com/bugzilla/">
SGI Bugzilla</a> database.
</p>

<h2><font face="ARIAL NARROW,HELVETICA">
Recent News
</font></h2>
<p>
<table border=0 cellspacing=2 width="100%">
<tr><td valign=top bgcolor="#88ee88"><font face="Helvetica, Arial">
2005/07/22
        </font></td>
        <td valign=top bgcolor="#99cccc"><font face="Helvetica, Arial">
		Merged all XFS fixes since SP1 into SLES9 SP2.
		Thanks Andreas!
        </font></td>
        </tr>
<tr><td valign=top bgcolor="#88ee88"><font face="Helvetica, Arial">
2005/06/03
        </font></td>
        <td valign=top bgcolor="#99cccc"><font face="Helvetica, Arial">
<A HREF="http://people.freebsd.org/~rodrigc/xfs/">XFS for FreeBSD</A> website
		announced (an independent porting effort not sponsored by SGI),
		supported by FreeBSD developers Craig Rodrigues and Alexander
		Kabaev.
        </font></td>
        </tr>
<tr><td valign=top bgcolor="#88ee88"><font face="Helvetica, Arial">
2004/10/26
        </font></td>
        <td valign=top bgcolor="#99cccc"><font face="Helvetica, Arial">
                XFS web pages updated for first time in several years. (*cough*)
        </font></td>
        </tr>
<tr><td valign=top bgcolor="#88ee88"><font face="Helvetica, Arial">
2004/10/17
        </font></td>
        <td valign=top bgcolor="#99cccc"><font face="Helvetica, Arial">
		Merged all XFS fixes since 2.6.5 into SLES9 Service Pack 1.
		Thanks Andreas!
        </font></td>
        </tr>
<tr><td valign=top bgcolor="#88ee88"><font face="Helvetica, Arial">
2004/02/18
        </font></td>
        <td valign=top bgcolor="#99cccc"><font face="Helvetica, Arial">
                XFS is merged into Marcelo's 2.4.25 kernel. 
        </font></td>
        </tr>
<tr><td valign=top bgcolor="#88ee88"><font face="Helvetica, Arial">
[Before-2004]
        </font></td>
        <td valign=top bgcolor="#99cccc"><font face="Helvetica, Arial">
                <a href="news.html">Older news...</a>
        </font></td>
        </tr>
</table>
</p>

<h2><font face="ARIAL NARROW,HELVETICA">
Features
</font></h2>
<p>
The XFS filesystem provides the following major features:
<br>
<br>

<ul>
<li>
<b>Journaling: Quick Recovery </b>

<br>
<br>
The XFS journaling technology allows it to restart very quickly
after an unexpected interruption, regardless of the number of files it is
managing.  Traditional filesystems must do special filesystem checks after
an interruption, which can take many hours to complete.  The XFS journaling
avoids these lengthy filesystem checks.
</p>
</li>

<li>
<b>Fast Transactions</b>
<p>
The XFS filesystem provides the advantages of journaling while
minimizing the performance impact of journaling on read and write
data transactions.  Its journaling structures and algorithms
are tuned to log the transactions rapidly.
</p>

<p>
XFS uses efficient tree structures for fast searches and rapid space
allocation.  XFS continues to deliver rapid response times, even for
directories with tens of thousands of entries.
</p>
</li>

<li>
<b>High Scalability</b>

<p>
XFS is a full 64-bit filesystem, and thus
is capable of handling files as large as a
million terabytes.

<pre>2<sup>63</sup>  = 9 x 10<sup>18</sup> = 9 exabytes </pre>
</p>

<p>
A million terabytes is hundreds of thousands of
times larger than most large filesystems in use today.
This may seem to be an extremely large address space, but it
is needed to plan for the exponential disk-density
improvements observed in the disk industry in recent years.
As the disk sizes grow, not only does the address space need to be
sufficiently large, but the structures and algorithms need to scale.
XFS is ready today with the technologies needed for this scalability.
</p>
</li>

<li>
<b>Excellent Bandwidth</b>
<p>
XFS as a filesystem is capable of delivering near-raw I/O performance.
XFS has proven scalability on SGI Altix systems of multiple
gigabytes-per-second on multiple terabyte filesystems.
</p>
</li>
</ul>
</p>

<h2><font face="ARIAL NARROW,HELVETICA">
Technical Specifications
</font></h2>

<p>
<b>Technology</b>
</p>
<p>
Journaled 64-bit filesystem with guaranteed
filesystem consistency.
</p>

<p>
<b>Availability</b>
</p>
<p>
XFS is available for Linux 2.4 and later kernels.
</p>

<p>
<b>Online Administration</b>
</p>
<p>
XFS supports filesystem growth for mounted volumes, allows
filesystem &quot;freeze&quot; and &quot;thaw&quot; operations to support
volume level snapshots, and provides an online file defragmentation
utility.
</p>

<p>
<b>Quotas</b>
</p>
<p>
XFS supports user and group quotas.
XFS considers quota information as filesystem metadata and uses
journaling to avoid the need for lengthy quota consistency checks
after a crash.
</p>

<p>
<b>Extended Attributes</b>
</p>
<p>
XFS implements fully journaled extended attributes.  An extended attribute
is a name/value pair associated with a file.  Attributes can be attached to 
all types of inodes:  regular files, directories, symbolic links, 
device nodes, and so forth.  Attribute values can contain up to 64KB of 
arbitrary binary data.  XFS implements three attribute namespaces: a user
namespace available to all users, protected by the normal file 
permissions; a system namespace, accessible only to privileged
users; and a security namespace, used by security modules (SELinux).
The system namespace can be used for protected filesystem meta-data 
such as access control lists (ACLs) and hierarchical storage manager
(HSM) file migration status.
</p>

<p>
<b>POSIX Access Control Lists (ACLs)</b> 
</p>
<p>
XFS supports the ACL semantics and interfaces described in the draft
POSIX 1003.1e standard.
</p>

<p>
<b>Maximum File Size</b> 
</p>
<p>
For Linux 2.4, the maximum accessible file offset is 16TB on 4K page size
and 64TB on 16K page size.  For Linux 2.6, when using 64 bit addressing in
the block devices layer (CONFIG_LBD), file size limit increases to 9
million terabytes (or the device limits).
</p>

<p>
<b>Maximum Filesystem Size</b> 
</p>
<p>
For Linux 2.4, 2 TB.  For Linux 2.6 and beyond, when using 64 bit addressing
in the block devices layer (CONFIG_LBD) and a 64 bit platform, filesystem
size limit increases to 9 million terabytes (or the device limits).
For these later kernels on 32 bit platforms, 16TB is the current limit
even with 64 bit addressing enabled in the block layer.
</p>

<p>
<b>Filesystem Block Size</b>
</p>
<p>
The minimum filesystem block size is 512 bytes.  The maximum
filesystem block size is the page size of the kernel, which is
4K on x86 architecture and is set as a kernel compile option
on IA-64 architecture.
</p>
<p>
Filesystem
extents (contiguous data) are configurable at file creation time using
fcntl and are multiples of the filesystem block size.  Single extents
can be up to 4 GB in size.
</p>

<p>
<b>Physical Disk Sector Sizes Supported</b>
</p>
<p>
512 bytes through to 32 kilobytes (in powers of 2), with the caveat that
the sector size must be less than or equal to the filesystem blocksize.
</p>

<p>
<b>NFS Compatibility </b>
</p>
<p>
With NFS version 3, 64-bit filesystems can be exported to other systems that
support the NFS V3 protocol.  Systems that use NFS V2 protocol may access XFS
filesystems within the 32-bit limit imposed by the protocol.
</p>

<p>
<b>Windows Compatibility</b>
</p>
<p>
SGI uses the Open Source Samba server to export XFS filesystems to Microsoft
Windows systems.  Samba speaks the SMB (Server Message Block) and CIFS
(Common Internet File System) protocols.
</p>

<p>
<b>Backup/Restore</b>
</p>
<p>
xfsdump and xfsrestore can be used for backup and restore of XFS file
systems to local/remote SCSI tapes or files.  It supports dumping of extended
attributes and quota information.  As the xfsdump format has been preserved
and is now endian neutral, dumps created on one platform can be restored
onto an XFS filesystem on another (different architectures, and even
different operating systems - IRIX to Linux, and vice-versa).
</p>

<p>
<b>Support for Hierarchical Storage</b>
</p>
<p>
The Data Management API (DMAPI/XDSM) allows implementation of hierarchical
storage management software with no kernel modifications as well as
high-performance dump programs without requiring &quot;raw&quot; access to
the disk and knowledge of filesystem structures.
</p>

<p>
<b>Optional Realtime Allocator</b>
</p>
<p>
XFS supports the notion of a &quot;realtime subvolume&quot; - a separate
area of disk space where only file data is stored.
Space on this subvolume is managed using the realtime allocator
(as opposed to the default, B+ tree space allocator).
The realtime subvolume is designed to provide very deterministic
data rates suitable for media streaming applications.
</p>


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