Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!gatech!udel!rochester!kodak!gizzmo!Kdavid From: Kdavid@gizzmo.UUCP (David Solan) Newsgroups: comp.sys.att Subject: Re: hard disk problems Summary: Removal of bad blocks Message-ID: <195@gizzmo.UUCP> Date: 15 Aug 88 06:21:32 GMT References: <15324@apple.Apple.COM> <19@zeno.MN.ORG> Organization: Objective Programming Inc. Lines: 88 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Many thanks to Gene H. Olson for his recent meticulous description of how to remove a bad block on the hard disk of the UNIX PC using the Diagnostic Floppy. Objective Utilities (TM), a software product of Objective Programming Inc., (Copyright (C) 1988 Objective Programming Incorporated, All Rights Reserved) can also accomplish this task on the UNIX PC (ALONG WITH MANY OTHERS), but in quite a different manner. Mr. Olson's method involves shutting down your system in order to do this bad block removal. It also involves doing complicated arithmetic. Objective Utilities involves neither of these. With Objective Utilities, the bad block (which, using a certain feature of Objective Utilities, you can readily map to the file it is in) is removed dynamically, while your system is up and running. After this removal, it is actually feasible to have a more sequentially organized file than you had previously with the bad block, and therefore a file that can be accessed more quickly by your hard disk, while with the Diagnostic Floppy bad block removal method, while seek times allegedly are not degraded after the removal (BUT SEE BELOW!), latency times certainly are. Actually, the /usr/adm/unix.log output only gives you information on a 1024 byte bad "block". If you remove both the 512 byte sectors comprising this bad block using Mr. Olson's method, as indeed he suggests (because in this situation you really have no other choice), seek times might indeed be degraded, since the second "bad" sector will have to be placed on a different track than the first "bad" sector (there's only room for one bad sector per track -- see below). Also, there is something I don't understand here and perhaps Mr. Olson could be so kind as to respond. Isn't it true that when you place a sector on the bad block table, via the Diagnostic Floppy for the UNIX PC, the actual data contents of the "bad" sector are NOT moved to the 17th sector of the track it is mapped to, so that data on that sector is lost forever if you do this? I was sure this was the case. Was I wrong? Can anyone answer this question absolutely, positively, for sure (no guesses here please!)? One last point in response to some earlier ruminations on USENET. The WD1010 method of sector verification when reading the hard disk depends on a certain layout for each track of the hard disk. The first 26 bytes is verification info. Then, for the next 17 sectors, we have 79 more bytes of verification info followed by 512 bytes of actual disk data, repeated 17 times. This comes to a total of 10073 bytes for 17 512-byte sectors, 16 of which are actually used in the UNIX file system or elsewhere for data (that is, 8192 bytes of actual data per track). Since the ST-506 drives used in this machine have 10416 raw bytes per track, this leaves an extra 343 bytes per track -- not enough to do anything in particular. Therefore, you CANNOT fit more than 17 sectors per track, at least not with the current STRICT limitations imposed on much of the hardware/software of the UNIX PC. If anyone on USENET wishes more information on Objective Utilities, or our other product for the UNIX PC, ACCUCLOCK, please send your FULL and EXACT USPS ADDRESS to the address below and brochures will be in the mail. You could also contact me by voice phone, as listed below, at any reasonable time, weekends included. P.S. While I am on the topic, let me get something publicly off my chest that has been gnawing away at me for some time. Objective Utilities is a fully copyrighted and trademarked product of Objective Programming Incorporated. We spent many long hours into the night to develop it. It belongs EXCLUSIVELY to us -- period. This is to notify anyone on USENET who might be using an illegal copy of this product, and unfortunately we have clear evidence that such activity was at least attempted by at least one person on USENET, that you are violating our rights if you are using it without a license to do so. Please IMMEDIATELY destroy ALL copies you have and preferably send us a personal notice that you are doing this. Of course, the product is available for a price to all who wish to pay for it. Multi-CPU licenses are also available. -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- David Solan Post Office Box 123 Norwalk, CT 06856 Voice: (203) 866-6900 attmail: -- 16 million Americans will die in the next 10 years without their seat belts on. Buckle up now! {codas,u1100a}-----\ David Solan rutgers!rochester!pcid!kodak!gizzmo!kdavid {lazlo,ethos,fthood}-----/