Novell Storage Services (NSS)

The Novell Storage Services file system is used in NetWare 5.0 and above, and most recently is open sourced and included in the SUSE Linux Enterprise Server (SLES) 9 SP1 Linux distribution and later (used in the Novell Open Enterprise Server Linux product).

The NSS file system is unique in many ways, especially in its ability to manage and support shared file services from simultaneous different file access protocols. It is designed to manage access control (using a unique model, called the Novell Trustee Model, that scales to hundreds of thousands of different users accessing the same storage securely) in enterprise file sharing environments.

NSS and its predecessor NWFS are the only file systems that can restrict the visibility of the directory tree based on the user ID accessing the file system. NSS and NWFS have built-in ACL (access control list) rights inheritance. NSS includes mature and robust features tailored for the file-sharing environment of the largest enterprises. The file system also scales to millions of files in a single directory. NSS also supports multiple data streams and rich metadata; its features are a superset of existing file systems on the market for data stream, metadata, name space, and attribute support.

Ext2

Ext2 does not maintain a journal, so it is generally not desirable to use it for any server that needs high availability, with one important exception. If the server is running as a Xen VM guest, you should format the /boot partition with Ext2 as explained in Paravitual Mode and Journaling File Systems in the Virtualization with Xen guide.

Ext3

The Ext3 file system is a journaled file system that has the widest use in Linux today. It is regarded by many in the Linux user community as the default Linux file system. It is quite robust and quick, although it does not scale well to large volumes or a great number of files.

A scalability feature has been added called H-trees, which significantly improved Ext3's scalability. However, it is still not as scalable as some of the other file systems. With H-trees, it scales similarly to NTFS. Without H-trees, Ext3 does not handle more than about 5,000 files in a directory.

Reiser

The Reiser file system is the default file system in SUSE Linux distributions. Reiser was designed to remove the scalability and performance limitations that exist in Ext2 and Ext3 file systems.

Reiser scales and performs extremely well on Linux, outscaling Ext3 with H-trees. In addition, Reiser was designed to use disk space very efficiently. As a result, it is the best file system on Linux where there are a great number of small files in the file system. Because collaboration (e-mail) and many Web servings applications have many small files, Reiser is best suited for these types of workloads.

XFS

The XFS file system is open source and is included in major Linux distributions. It originated from SGI (Irix) and was designed specifically for large files and large volume scalability.

Video and multimedia files are best handled by this file system. Scaling to petabyte volumes, it also handles very large amounts of data. It is one of the few file systems on Linux that supports HSM data migration.

File Serving (NAS)

Generally there are two types of NAS use cases: Serving files to application servers in a tiered service oriented architecture (SOA), and serving files to end user desktops and workstations. The former has minimal access control requirements. The latter has quite heavy access control requirements.

Typically for serving files to application servers (traditional NAS), you would choose a file system that is scalable and fast. Reiser and XFS would be good choices in this environment. For file serving to end user workstations, the access control and security management capabilities of the NSS file systems with CIFS and NCP file access protocols are important.

The NSS model does better than the other file systems for very large numbers of users. It allows for security between users and also allows for very fine granular sharing between given users and groups. NSS includes a visibility feature implemented in the file system that prevents unauthorized users from even seeing subdirectory structures they don't have rights to access.

Network Printing (iPrint)

iPrint is file system agnostic. There is no noticeable difference in performance or reliability on any of the file systems.

iFolder

Novell iFolder does not depend on a particular file system. Based on the client workload, the file system should be chosen at the server side. Because it mostly serves user data, a file system that can scale with a large number of files is the best suited in most deployments, making Reiser and NSS the best bets. Novell iFolder maintains its own ACL, so having an NSS file system that supports a rich ACL might be redundant.

GroupWise

GroupWise deals with many little files. Because only the application process is accessing the file system, the added overhead of the rich ACL and file attributes found in NSS is redundant. The necessary characteristics are a file system whose performance remains relatively constant regardless of the number of files that are in the volume, and that performs well with small files. Best bets would be ReiserFS, XFS, and NSS. Ext3 does not handle large systems well (where you have more than 10,000 files in the system).

Novell Cluster Services

Although Novell Cluster Services does not depend on a particular file system, you must use the same file systems from node to node. For example, if you are using NSS on one node, you need to use NSS on the failover node as well.

Dynamic Storage Technology

Dynamic Storage Technology does not depend on a particular file system in principle; however, it is currently supported only on NSS volumes.

Novell plans to add support for additional file systems in the future. When that happens, it will be important to remember that file systems cannot be mixed between volumes and shadow volumes. For example, if you choose to shadow an NSS volume, the secondary volume must also be NSS.