Ramdisk Release Notes for HP-UX 11i v2

Announcement
Ramdisk is emulation of disk in system memory. Accessing files on a Ramdisk is much
faster than accessing files on a real disk. This is especially useful for applications that
use intermediate temporary files frequently. Applications can access files on a Ramdisk
in a way that is similar to accessing files on a hard disk. However, the data saved on
the Ramdisk is not persistent across reboots.
The patches, PHKL_37170 and PHCO_37169 enable you to create a swappable disk
or a non-swappable disk. Creation of a Ramdisk instance (swappable or non-swappable)
creates two device files /dev/dsk/ram<volume_number> and /dev/rdsk/
ram<volume_number> on the system. For more information about creating a Ramdisk
instance, see “Creating and Deleting a Ramdisk Instance”.
Swappable Ramdisk allocates the user space process memory to create swappable
Ramdisk instance on the system. A swappable Ramdisk instance enables users to share
the configured system memory with other applications. The virtual size of a swappable
Ramdisk instance can be greater than the size of the available physical memory size.
A non-swappable Ramdisk instance does not allow users to share the configured system
memory with other applications.
Features and Benefits
This section discusses the features and benefits that Ramdisk offers.
Features
Ramdisk supports the following features:
• Swappable and non-swappable Ramdisk.
• Up to 14 Ramdisk instances simultaneously.
• The Veritas File Systems (VxFS) and Logical Volume Manager (LVM) without
mirrors.
• The online performance diagnostic tool, Glance. You can view the Ramdisk I/O
statistics using Glance.
• The ioscan and diskinfo commands.
• The recovery of Ramdisk configuration across system reboots. The Ramdisk
configuration is saved in the /etc/ramdsktab file. This file is updated when a
Ramdisk instance is created or destroyed.
NOTE: The file /etc/ramdsktab is modified internally by the system, using
the ramdisk utility. This file must not be edited by the super user.
• Configuration of Ramdisk using the System Administration Management (SAM)
application.
6 HP-UX Ramdisk Release Notes