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HP-UX 11iv3 Memory File System 3.0

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HP-UX 11iv3 Memory File System (MemFS) 3.0

A Memory-based File System (MemFS) is a file system that resides in primary memory. It does not normally write data out to stable storage. MemFS is able to provide extremely high throughput.  The purpose of such a file system is to provide fast access for temporary or short lived files that do not need to be kept for an indeterminate time. All file types are supported, including symbolic links and block and character special device files. MemFS uses system swap device to store the data on the file systems. Multiple MemFS file systems can be mounted on a single system, but they all share the same resources, kernel memory and system swap device.

What Is New In This Release?

This release of Memory File Sysetm (MeMFS) 3.0 does not provide any new feature.

What Is New In Memory File System (MemFS) 2.0 Release?

    New mount options have been added to modify the permissions and ownership of root of the file system during mount. This will eliminate the need to modify the permissions/ownership of root after every mount. New options introduced are:

  1. mode: Permissions to be set for the root of the file system after mounting.

  2. user: User ID or login name to be the owner of the root of the file system after mount.

  3. group: The group ID or group name to be the owning group of the root of the file system after mount.


In addition following are the features of MemFS on 11iv3 compared to MemFS on 11iv2:

  • A new light weight layout. Thus performs better than MemFS on HP-UX 11iv2 (by a factor of 2).

  • Support for very large file and file system sizes (Currently tested till 300GB).

  • No limitation on the number of MemFS instances.

  • Number of files on a file system can be restricted, if needed.  

  • File system size can be restricted or can be allowed to grow depending on the swap space available.

  • Swaps data on to system swap device efficiently.

  • Support for large files.

  • Maximum amount of memory and swap that can be used by MemFS can be tuned.

  • Access Control Lists (ACLs) and quotas are not supported.

What Is In This Depot?

The depot delivers MemFS bundle (revision: B.11.31.03) and other needed patches. MemFS bundle delivers the kernel module and commands in the following products:

  1. MemoryFSKern, revision=B.11.31.03

    This delivers the kernel module, memfs which provides the file system functionality. This module implements all the basic file and file system operations. The metadata of MemFS is stored in the kernel memory and data in the MemFS files are stored in the system swap by the kernel. Maximum amount of memory and swap that can be used by MemFS can be tuned.

  2. MemoryFSCmd, revision=B.11.31.03

    Delivers the commands needed to access MemFS file systems, mount(1m) and umount(1m).

Features and Benefits

         Supports creation of large file system and files. Tested till 300GB.

         MemFS can co-exist with other memory based file systems like RAMdisk.

         Improved response time due to reduced overhead of writing structural changes to disk.

         Improved performance when predominant operations are metadata operations and, the application creates large number of temporary files.

         New light weight layout allows faster access for temporary files that do not need to be stored for a long time.

         MemFS provides additional file system space, and supports UNIX file semantics while remaining fully compatible with other file system types.

         Page-able memory based file system, which transparently uses the system swap device when there is system memory pressure.

         Supported by Ignite-UX (Ignite-UX release C.7.2 onwards)

         Supported by HPE GlancePlus C.04.70.000 to monitor memory/swap usage by MemFS

         Supported by sar (SAR-MEMFS) to monitor memory/swap usage by MemFS

Product Documentation

For more information on HP-UX Memory File Systems, see "HP-UX 11iv3 Memory File System Administrator's Guide".

Additional product information
Product #: MemFS11iv3
Version: 3.0
Software specification: HP-UX 11.31 IA/PA(MemFS_B.11.31.03_HP-UX_B.11.31_IA_PA.depot)