steve@avalon.dartmouth.edu (Steve Campbell) (08/23/89)
Does Ultrix 3.1 (RISC) perform automatic bad block forwarding (revectoring) on SCI disks such as RA90's? What strategy is used? Does anything prevent runaway forwarding in the instance of false bad block errors that are caused by other electronic failures? Steve Campbell Dartmouth College
alan@shodha.dec.com ( Alan's Home for Wayward Notes File.) (08/23/89)
In article <15164@dartvax.Dartmouth.EDU>, steve@avalon.dartmouth.edu (Steve Campbell) writes: > Does Ultrix 3.1 (RISC) perform automatic bad block forwarding (revectoring) > on SCI disks such as RA90's? What strategy is used? Does anything prevent > runaway forwarding in the instance of false bad block errors that are caused > by other electronic failures? > Steve Campbell > Dartmouth College Well first the RA90 isn't a SCSI disk. In V3.0 and V3.1 the SCSI support doesn't include dyanmic BBR. There is a program called rzdisk that will let you do this by hand. I wouldn't be suprised if a future version supports dynamic BBR in the SCSI drivers. The DECsystem 5400 and 58xx, which run V3.1, use the KDA50, KDB50, HSCxx and other DSA controllers do support dynamic BBR. The exact stratagy varies from disk to disk, but on most of the disks there is one extra sector per track that is used for revectoring. Some disks may have more than one. Except for the time I tried to use an RD52 that was unformatted I've never seen "runaway BBR". I don't know if there is anything built into the algorithms to watch for this, but in the worst case the control tables on the disk will fill up or become corrupted you'll see messages like: Unit x write protected. Backup media and reformat. I don't remember if this was catastrophic electronic failure or a head crash, when it happened to me. There weren't that many blocks that had been revectored, though. -- Alan Rollow alan%nabeth.dec.com@decwrl.dec.com
steve@avalon.dartmouth.edu (Steve Campbell) (08/24/89)
In article <388@shodha.dec.com> alan@shodha.dec.com ( Alan's Home for Wayward Notes File.) writes: >In article <15164@dartvax.Dartmouth.EDU>, steve@avalon.dartmouth.edu (Steve Campbell) writes: >> Does Ultrix 3.1 (RISC) perform automatic bad block forwarding (revectoring) >> on SCI disks such as RA90's? ^ Sorry, I fat-fingered that. I meant to say SDI (Standard Disk Interconnect?). My understanding is that disks using SDI also use the Mass Storage Control Protocol and are controlled by the UDA/KDB family of controllers. As Alan says, the answer to my question is yes. Thanks. Steve