Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!zaphod.mps.ohio-state.edu!magnus.acs.ohio-state.edu!csn!seri!wind55!marshall From: marshall@wind55.seri.gov (Marshall L. Buhl) Newsgroups: comp.sys.ibm.pc.hardware Subject: Re: Drive Arrays Message-ID: Date: 8 Apr 91 18:29:04 GMT References: <46563@ut-emx.uucp> Sender: news@seri.gov (news) Distribution: na Organization: Solar Energy Research Institute Lines: 64 solomon@chaos.utexas.edu (Thomas Solomon) writes: > I recently received some product information from Dell computers. >They claim to have a controller that they refer to as the "Dell >Drive Array" that can handle up to 10 disk drives at the same time? >I get the impression from their information that this controller can >actually write to these different disks _at the same time_, allowing >blazing fast disk access. > Does anyone know about these drive arrays or about anyone elses >drive array. Presumably, with multiple disks operating simultaneously, >you should be able to get _continuous_ disk storage rates up to a >few MB/sec. I have looked at both the Dell drive array and the one that is an option on the Compaq SystemPro. They have several similarities. Both can "data stripe" to multiple drives simultaneously. Your data is broken up and stored on several drives. This means you're not limited to the transfer rate of a single drive. You're limited to the transfer rate of the EISA bus which is 32-bits wide. Both provide data guarding. On the Dell drive array, your data is striped on four disks with a fifth for parity. Thus, if one of your drives fails, the others will still contain all the data. The system will continue to run, but slower. When you get a replacement disk, take down the system and install it. The data will be restored to it from the other disks in the background while the machine goes back to its normal business. I think they can also provide disk mirroring, where two copies of your data are stored on different drives. I believe the differences are in performance. The Dell uses an i960 RISC processor and the Compaq uses an old 80186. IMO, this is the best argument I've seen for an EISA bus. I've heard that Dell has just started shipping their array, but in very small quantities. I was told that this was so that their support techs could get trained for it before mass shipping starts. From my Dell 1991 catalog: i960 @ 16 MHz 32-bit EISA interface 256K SRAM for local data storage i82355 bus master interface chip Up to 10 drives 33 MB/sec burst transfer rate SCSI drives are 200MB IDE drives w/ 16 msec average seek (Conner) works with DOS, OS/2, Unix, Vines and NetWare You will need an auxiliary power supply for more than 7 drives on the Dell. This will change after Dell uses up all their older power supplies and bigger ones are installed as standard equipment on their tower systems. -- Marshall L. Buhl, Jr. EMAIL: marshall@seri.gov Senior Computer Engineer VOICE: (303)231-1014 Wind Program 1617 Cole Blvd., Golden, CO 80401-3393 Solar Energy Research Institute Solar - safe energy for a healthy future