A ramdisk ( or ramdisc ) filesystem stores data directly to memory instead of a hard disk drive providing the fastest data I/O available to increase performance of applications. All of the standard hp-ux data access commands are compatible with ramdisc filesystems. Why is a ramdisc faster than a conventional disk drive? A ramdisc has no mechanical moving parts and all data is stored in main system memory. A disk drive stores data on platters that spin at a high rpm with read and write heads that move across a set of platters to access the data. The animated image represents the method that data is retrieved. Move your mouse over the disk drive to start the animation. The red colored dots represent a request for data. The drive heads read the VTOC ( Volume Table Of Contents ) then move to a location on the platter where the data is stored. Depending on rotation, the read head may have to wait for another revolution before it can read or write any of the data on the platters. The yellow colored dots represent the data being sent back to the system. If you remove the mechanical limitations by using a solid state disk, your performance will improve but not to the degree of a ramdisc due to SCSI bus or PCI bus speeds as compared to the speed of a memory bus. The image on the right is a disk drive with the top cover removed. Your data is more than likely not stored sequentially on the platters so there are delays within a busy disk drive to retrieve or write the data as well.
What happens to a ramdisc filesystem when the power goes out? In the past, this question may|
have been more difficult to answer. Most users want to have that "warm and fuzzy feeling" that the data
is safe and secure which usually tends to sacrifice speed for security. Using the security advantages of
MirrorDisk/UX combined with the speed of a ramdisc, you can now have both speed and data integrity
using our software package referred to as RamDisc Plus.
The RamDisc Plus package ¹ allows you to:
The RamCluster package (part of RamDisc Plus) allows you to:
¹ RamDisc Plus contains all of the functionality of RamDisc Classic.
² MirrorDisk/UX is an optional software product from Hewlett-Packard.
³ MC/ServiceGuard is an optional software product from Hewlett-Packard.
RamDisc Plus is available for download here and FAQs are available here. Updated URLs
RamDisc pricing is based upon the memory range of usage shown in the chart below. A new tool has
been developed to provide flexible pricing based upon the actual amount of memory (in 1GB portions)
reserved for RamDisc configurations. This tool also calculates a future RamDisc upgrade as well as
multiple sysytem discounts and supports memory ranges up to 512GB (using HPUX 11.23 11i v2 ).
|RamDisc Usage||¹||GigaBytes||Purchase Price||Support Price||²|
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