*Note: This section is a slightly trimmed and editted version of the SSD FAQ from Robert at DES (rdavid@ccmgate.mti.com) which I think he also posts to c.d.sybase. I would take the "up to 1000 times faster" claim with a grain of salt, though the general info is good. --rdv, 94/9/15
1) Q. What are solid-state disk emulators?
A. Simply put, solid-state disk emulators are Dynamic Random Access Memory (DRAM)-based storage devices that appear to the host exactly as a magnetic rotating disk. DRAM chips, which are ultra-fast devices that store data while the system is on, increase data access, thereby eliminating I/O bottlenecks that constrain overall system performance.
Solid-state disk emulators can be either volatile or non-volatile, meaning that they are able to retain data when the system is turned off. DRAM alone is volatile. Solid-state disk emulators that are designed with an integrated backup system are non-volatile storage devices; if a power outage occurs, the user's data is protected by the backup system and will not be lost. Solid-state disk emulators are volatile when methods for backing up data are absent. A power failure will cause data to be lost on a volatile solid-state disk.
2) Q. How do solid-state disk emulators work?
A. Solid-state disk emulators plug into a computer's I/O controller. Typical client/server systems use the ANSI-standard SCSI interface on its I/O controller. It is plug-and-play because it emulates a rotating disk. No special drivers or operating system patches are required to make it work. In addition, because there are no moving parts, seek and rotational latency times are zero, which aids solid-state disk emulators in performing up to 1000 times faster than magnetic rotating disk drives.
3) Q. What applications are well-suited for Solid State Disk?
A. In general terms: 1) transaction processing, 2) batch processing, and 3) query or decision support analysis. Many types of application software can take advantage of the super-fast access times SSD offers.
4) Q. How reliable are Solid State Disks?
A. Based on real world user data from a large SSD site, the actual power on hours mean-time between failure is greater than 1,000,000 hours. Since this site has yet to have a failure, the number is likely to go up.
email me at rdv@isi.edu
Copyright 1996 Rod Van Meter