Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!vsi1!octopus!pete From: pete@octopus.UUCP (Pete Holzmann) Newsgroups: comp.sys.ibm.pc Subject: Re: Spinrite Concerns Message-ID: <333@octopus.UUCP> Date: 25 Aug 88 05:49:25 GMT References: <329@octopus.UUCP> <663@starfish.Convergent.COM> Reply-To: pete@octopus.UUCP (Pete Holzmann) Organization: Octopus Enterprises, Cupertino CA Lines: 57 In article <663@starfish.Convergent.COM> cdold (Clarence Dold) writes: >From article <329@octopus.UUCP>, by pete@octopus.UUCP (Pete Holzmann): >> 2) Actual surface defects on the disk will be found by the SpinRite >> thorough testing. It is a more intense test than drive >> manufacturers use for the most part! >Whoa, there! >Disk Manufacturers can and generally do perform two types of test that you >could never touch in the field: > 1) Analog testing, to check for physical dropouts. This doesn't > even use drive electronics, I don't see how you could duplicate it. > 2) Reduced margin testing. Lower the write current during pattern > generation, reduce read gain during pattern checking. This is is why I left in the 'for the most part'. What disk manufacturers generally don't do is extensive worst-case pattern testing, especially with your particular controller+drive combination. Is analog testing really in common use now on shippable drives? Seems like it would be tough to correlate the analog results with cylinder/byte# info, unless the analog test is using the normal head for testing. If so, it isn't going to find between-track problems any better than a good worst-case pattern test. In general, doing your testing 'beyond spec' is something that can't be field duplicated, it is true. On the other hand... >Both of these methods yield reported defects that you will **NEVER** catch >regardless of how clever your techniques might be. The only way you might >see them is through media aging, which is what they are trying to predict. >What you will catch are solid defects. Listen very carefully while >doing the format. WD1010-001 chips would perform four retries before >reporting a 'soft' error. What SpinRite (and Disk Technician) does is disable all retries. If there is a single error somewhere on a freshly written test pattern, it marks it bad. Thus, any area of the disk that is marginal enough to be detected at *all* by the drive electronics (note that around 80 different worst case patterns are used), will be marked bad. I've got people who have been running on a SpinRite-d drive since Christmas without any additional defects showing up. That's on drives that had been in very bad shape before. Low level formats should be refreshed pretty often in any case (more than once a year, I think. SpinRite recommends every 3 months or so.) >Give up the badspots. Don't play games with the future of your data. >Particularly, watch for bad spots mapped on the same head, same sector, >on adjacent tracks. Radial Striation is a common defect. Note that not doing a low level reformat at regular intervals is more certainly bad for your data than worrying about latent defects that currently don't even cause a soft error. Thus, if you re-do the low level format as you should, you will also find any emerging latent defects. And if you *don't* redo the low level format, you'll be bitten by that problem long before the latent defects emerge! Pete -- OOO __| ___ Peter Holzmann, Octopus Enterprises OOOOOOO___/ _______ USPS: 19611 La Mar Court, Cupertino, CA 95014 OOOOO \___/ UUCP: {hpda,pyramid}!octopus!pete ___| \_____ Phone: 408/996-7746