Path: utzoo!utgpu!attcan!uunet!ibmpa!saare
From: saare@ibmpa.UUCP (John Saare)
Newsgroups: comp.sys.amiga.tech
Subject: FFS: The beating goes on...
Keywords: ffs fragile diskdoctor
Message-ID: <695@ibmpa.UUCP>
Date: 18 Jan 89 23:50:52 GMT
Organization: IBM TCS Development, Palo Alto
Lines: 93

First off, I'd like to thank David Gay for giving my problem some
thought and pointing out some deficiencies in my original posting...

A question to C-A is at the end of this note...

*** LONG APPEND WARNING ***

This is an elaboration of the question I asked earlier in
comp.sys.amiga.  This is the scenario:
  The hardware:
    A500
    Pac. Periph. SubSystem 500
    Pac. Periph. Overdrive host adapter
    Micron 2MB 
    Adaptec 4000A SCSI to ST-506 xlator.
    2x70MB disks (ST-506)(Only 1 is relevant).
  
  The events:
    - My Micron 2MB flakes out and is sent off for repair, so I'm running
      with 512KB.
    - Using PP(Pac. Periph.) utilities of unknown vintage, but that are
      at least 1.3 cognizant, I perform a low-level format of a drive
      with an interleave of 2.  NOTE: There is no defect list available
      for the drive.  The format completes with no errors reported.
    - Using PP utilities, a surface scan is performed.  No errors are
      reported.
    - A mountlist entry is built for the drive.  I've heard that Interleave
      should be set to 0 for a 1:1, 1 for a 2:1, etc....  I've tried
      setting it to both n and n-1.  Results appear identical.  I've
      tried deleting MaxTransfer and setting it to arbitrarily large
      numbers e.g., 10000.  Because I'm using (was using) the Micron board, I've
      set Mask to 7ffff to prevent DMA to fast RAM.  I've tried
      removing the Micron board altogether (see above).
      Other mountlist fields are left as the PP utilities created them and/or
      as the C-A dox suggest.
      In essence, the mountlist entry for DH0: describes a single partition
      encompassing the entire disk.
    - I boot under 1.3 and issue the commands:
       mount dh0:
       format drive dh0: name "SlowBirds" ffs
    - The file-system format completes with NO errors, i.e., "verifying"
      never complains.  It is known that there are errors on this drive, but
      not where.  It's annoying that NONE of these errors have been caught
      up to this point.
    - The system runs but disk xfer rates are very slow e.g. 27K/sec ala
      diskperf.  Nothing I do improves disk performance.
    - I install stuff and grumpily procede as normal.
    - One day, while compiling (Manx 3.6a for the detail freaks) I get
      a R/W error on volume "SlowBirds".  I select cancel and then
      quarantine the whole directory the error occurred in, using "protect".
    - I cross my fingers and continue to use the system over a period of
      several days.  The system is rebooted before each day's use.  Everything
      seems fine.
    - One day, the machine crashes as a result of an out of memory condition.
    - Upon reboot, the disk-validator is run and WILL NOT GET PAST the 
      allocated bad blocks, so I'm left with an invalid, read-only disk.
    - I wait until the Micron board returns (kudos to Micron for fast and
      efficient service), re-install it and run DiskDoctor.  After ALL
      this hoopla, the disk-validator is STILL unable to validate the
      disk, running into the bad blocks and failing to procede.

I've become disgusted and re"format"ted the whole mess.  I'm sure the problem
will repeat itself.  So some questions (some are semi-rhetorical):

    - It appears as though if a file-system is EVER formatted with ANY
      bad blocks, you will be scr_w_d(I'll buy a vowel Vanna). Is this true?
    - The verification step of "format" appears to be mostly a waste
      of cycles, doesn't it?
    - Given I don't have a practical means of USENET down-loading, are
      there any PD(Fish) or commercial utilities that will allow AmigaDOS/FFS
      to cope with bad blocks?  David Gay mentioned that Disk Mechanic
      might do the trick but has problems.  Unfortunately I'm unable to
      download David's own utility.
    - Has anybody experienced throughput problems with the Overdrive/Adaptec
      4000a combo?  Any solutions? 
    - If I ever get a working system again, I'll be willing to write a 
      utility that addresses EXACTLY this problem.  Anybody interested?
    - This last one is addressed to C-A:  I know my system is not
      of standard configuration.  I know of several difficulties with
      the PP host adapter and software aka software.  I know of the
      difficulties with interactions between the Micron 2MB and other
      boards such as the PP host adapter.  I believe that I've experienced a
      problem that is generic to potentially all AmigaDOS hard-disk
      installations.  Others have experienced similar problems I'm sure.
      The potential bandwidth of FFS is something to be proud of.
      I'm sure my problem here has to do with either PP software or
      my own ineptitude.  The robustness of FFS (and "OFS") should
      be of concern.  Effectively, permanently invalidating an entire
      70MB filesystem because of a few bad sectors just isn't cricket!
      Don't you agree?

My thanks to anybody who slogged through this note.  Any and all (polite)
suggestions will be appreciated.  -- John Saare (uunet!ibmsupt!saare)