In a message dated 9/28/2006 12:39:28 P.M. Central Daylight Time, [EMAIL PROTECTED] writes:
>SLED (Slow Large Expensive Disks). Ca. 1988 several engineering students at the University of California in Berkeley published an article (I think it was in an IEEE journal) describing their experiments to create a Redundant Array of Inexpensive Disks (RAID) in order to counter what they saw as negative trends in disk storage, which were larger and larger amounts of storage within one control unit and whose cost was steadily increasing. They devised several schemes in which one such large expensive disk drive (e.g., a 3390 controlled by a 3990) could be functionally replaced by several (an array of) small personal computer-type hard drives with the necessary fault-detection and -correction mechanisms inherent to the 3990 provided by having the data stored on more than one disk (redundant). More logic was also required to translate IBM CCWs into commands that would work with the small hard drives on SCUSI channels instead of Multiplexor or ESCON channels and to translate the disk's ending status back into S/390 channel-compatible protocols. Since the small hard drive was much less expensive than a single large disk drive, they used the word inexpensive in their acronym. The concepts were quickly pounced upon by most of the DASD vendors, and ultimately incorporated into all new DASD products by all vendors. IBM's 3390 was the last non-RAID disk made by any vendor. IBM now sells virtual 3390s only. Not wishing to emphasize the inexpensive aspect of their new products, the vendors replaced "inexpensive" with "independent" so the acronym RAID could be retained without losing any sales when customers might ask "Why is your Redundant Array of Disks not very Inexpensive?" The alternative of a RAID became known as a Single Large Expensive Disk (SLED). Bill Fairchild ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
