Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!rpi!crdgw1!sixhub!davidsen From: davidsen@sixhub.UUCP (Wm E. Davidsen Jr) Newsgroups: comp.sys.ibm.pc.hardware Subject: Re: Disk Arrays (Was: ISA boards, EISA bus) Message-ID: <2013@sixhub.UUCP> Date: 2 Oct 90 02:38:51 GMT References: <1471@gold.GVG.TEK.COM> <1477@gold.GVG.TEK.COM> <5777@holston.UUCP> <1970@sixhub.UUCP> <48109@bigtex.cactus.org> Reply-To: davidsen@sixhub.UUCP (bill davidsen) Organization: *IX Public Access UNIX, Schenectady NY Lines: 33 In article <48109@bigtex.cactus.org> james@bigtex.cactus.org (James Van Artsdalen) writes: | (Hopefully I didn't take Bill's comments too far out of context) I have no complaints. | Actually, a key goal of data guarding is to keep running in the event | of a failure. For example, with the Dell drive array, you can have a | drive completely fail (yank the power cable out) without any errors. [ ... ] | Until the defective drive is replaced, there is no data guarding and | performance is reduced. I guess I sounded as though the whole thing would be dead with one drive down. If you can afford to run with no guarding you can keep going. This sounds somewhat like doing a XOR of all the sectors on N disks and writing the result sector to the N+1 disk. You can also do it with schemes like Hamming or fire codes (error recovery schemes). In any of these methods you can run doing error recovery on every read, and I hope I didn't mislead anyone on that. *I* wouldn't want to, but I am highly paranoid. By the time you buy a machine with N+1 drives and a fancy controller, and decide to leave one Nth of your capacity for error protection, you probably will spend enough to have a spare drive on site, tested, formatted, and ready to drop in and run. -- bill davidsen - davidsen@sixhub.uucp (uunet!crdgw1!sixhub!davidsen) sysop *IX BBS and Public Access UNIX moderator of comp.binaries.ibm.pc and 80386 mailing list "Stupidity, like virtue, is its own reward" -me