bhnnessy@swift.cs.tcd.ie (12/05/90)
I am investigating the viability of a RAID(Redundant Array of Inexpensive Disks)system. This would require the connection of about 20 disks. However only a few SCSI addresses are available to connect the system. To get around this problem I was wonder Any help on this matter would be much appreciated. Bryan Hennessy, bhnnessy@cs.tcd.ie University of Dublin, Trinity College, IRELAND. #! rnews 1472 Relay-Version: VMS News - V6.0 13/10/90 VAX/VMS V5.2; site swift.cs.tcd.ie Path: swift.cs.tcd.ie!vax1.tcd.ie!dcmcrthy Newsgroups: rec.scuba Subject: Query - PRICES Message-ID: <1990Dec4.154022.7348@vax1.tcd
israel@mitisft.Convergent.COM (Paul Israel) (12/06/90)
In article <1990Dec4.175834.7595@swift.cs.tcd.ie> bhnnessy@swift.cs.tcd.ie writes: >I am investigating the viability of a RAID(Redundant Array of Inexpensive Disks)system. This would require the connection of about 20 disks. However only a few SCSI addresses are available to connect the system. To get around this problem I was wonder >Any help on this matter would be much appreciated. As I understand it, SCSI standards define an option called a LUN, or "Logical Unit Number", which is provided as an three bit field in SCSI command headers. Apparently, this field, in combination with a SCSI address, is used for accessing up to 256 separate devices on one SCSI bus. To use this, eight devices are accessed through a single SCSI controller interface, thus using up only one SCSI address. A typical configuration might consist of a single SCSI-to-ESDI controller, which in turn would talk to eight ESDI hard disks. All eight disks are accessed via the same SCSI address, but different LUN's. The other 7 SCSI addresses are then still available for other combinations of devices. Three such controller/ disk configurations on the same SCSI bus would then give you 24 disks. I'm afraid I can't point out a specific vendor who's implementing these features, but I'd be very surprised if someone somewhere isn't doing it. This would appear the most efficient solution to your problem. -- Paul Israel Renegade Systems, 434 South Bernardo Ave, #2 Sunnyvale, CA 94086 Disclaimer: "Who, me? I wasn't even there!" ctnews!mitisft!hamster!israel