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Date:      Sat, 21 Oct 2000 21:16:56 -0700
From:      "John W. De Boskey" <jwd@FreeBSD.org>
To:        freebsd-current@FreeBSD.org
Cc:        Peter Wemm <peter@FreeBSD.org>
Subject:   newfs/fsck problem (bad superblocks)
Message-ID:  <20001021211656.A62615@FreeBSD.org>

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Hi,

   I posted a question concerning fsck yesterday. A number of
people replied with the 'bad harddisk' comment.

   I have followed up some more on the problem, and can now
reproduce it on different filesystems.

   Below, I umount my /usr/obj, newfs it, mount it, unmount
it, and then fsck it. The fsck complains about a bad superblock.
Also, do not remotely reboot after this if the newly newfs'd
filesystem is automounted in /etc/fstab. The boot process
will hang waiting for fsck to be run manually.

   Example:

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%umount /usr/obj
%newfs /dev/ccd0a
Warning: 1616 sector(s) in last cylinder unallocated
/dev/ccd0a:     6666672 sectors in 1628 cylinders of 1 tracks, 4096 sectors
        3255.2MB in 102 cyl groups (16 c/g, 32.00MB/g, 4096 i/g)
super-block backups (for fsck -b #) at:
 32, 65568, 131104, 196640, 262176, 327712, 393248, 458784, 524320, 589856,
 655392, 720928, 786464, 852000, 917536, 983072, 1048608, 1114144, 1179680,
 1245216, 1310752, 1376288, 1441824, 1507360, 1572896, 1638432, 1703968,
 1769504, 1835040, 1900576, 1966112, 2031648, 2097184, 2162720, 2228256,
 2293792, 2359328, 2424864, 2490400, 2555936, 2621472, 2687008, 2752544,
 2818080, 2883616, 2949152, 3014688, 3080224, 3145760, 3211296, 3276832,
 3342368, 3407904, 3473440, 3538976, 3604512, 3670048, 3735584, 3801120,
 3866656, 3932192, 3997728, 4063264, 4128800, 4194336, 4259872, 4325408,
 4390944, 4456480, 4522016, 4587552, 4653088, 4718624, 4784160, 4849696,
 4915232, 4980768, 5046304, 5111840, 5177376, 5242912, 5308448, 5373984,
 5439520, 5505056, 5570592, 5636128, 5701664, 5767200, 5832736, 5898272,
 5963808, 6029344, 6094880, 6160416, 6225952, 6291488, 6357024, 6422560,
 6488096, 6553632, 6619168
%mount /dev/ccd0a /usr/obj
%df -m /usr/obj
Filesystem  1M-blocks     Used    Avail Capacity  Mounted on
/dev/ccd0a       3201        0     2944     0%    /usr/obj
%umount /usr/obj
%/sbin/fsck -y /dev/ccd0a
** /dev/ccd0a
BAD SUPER BLOCK: VALUES IN SUPER BLOCK DISAGREE WITH THOSE IN FIRST ALTERNATE

LOOK FOR ALTERNATE SUPERBLOCKS? yes

USING ALTERNATE SUPERBLOCK AT 32
** Last Mounted on 
** Phase 1 - Check Blocks and Sizes
** Phase 2 - Check Pathnames
** Phase 3 - Check Connectivity
** Phase 4 - Check Reference Counts
** Phase 5 - Check Cyl groups
1 files, 1 used, 1638914 free (18 frags, 204862 blocks, 0.0% fragmentation)

UPDATE STANDARD SUPERBLOCK? yes


***** FILE SYSTEM WAS MODIFIED *****
%
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++



    I am wondering about the following patch :

peter       2000/10/16 17:41:37 PDT

  Modified files:
    sbin/newfs           mkfs.c
  Log:
  Implement simple write combining for newfs - this is particularly useful
  for large scsi disks with WCE = 0.  This yields around a 7 times speedup
  on elapsed newfs time on test disks here.  64k clusters seems to be the
  sweet spot for scsi disks using our present drivers.

  Revision  Changes    Path
  1.30      +38 -1     src/sbin/newfs/mkfs.c



    I will revert this patch tomorrow. I also wonder if this is related
to the 'make release' problems.


    Comments welcome.

-John


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