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TechNotes
-----------------------------------------------------------------
Bulletin Number: 222-3
Date: 13 August 1991
Summary: Fix for 4.10 file system inconsistency problem
Server: All
Software Version: 4.10 (0) and 4.10 (1)
Category: VINES
-----------------------------------------------------------------
PROBLEM:
A problem has been identified in VINES Revision 4.10 that in certain cases
can cause inconsistencies in the file system. The problem is unique to
VINES 4.10 (0) and is related to a specific set of file system operations and
environments.
The problem occurs when the end of a file that is larger than 266KB is
truncated and the file is reduced to a size that is equal to or less than
266KB. When the reduced file is written to disk, there is a small possibility
that the data blocks that are no longer needed are not released properly.
The problem occurs only if these data blocks are reallocated before the
original file is deleted. If the data blocks are released properly, then no
inconsistencies occur in the file system.
This problem may occur on any server running VINES 4.10 (0), including servers
that have applied the 4.10 (1) Applications Toolkit patch. This problem does
not occur on servers running VINES 3.x or 4.00, for example 4.00 (5).
Note: The 222-3 version of this technical bulletin obsoletes any
previous version.
SYMPTOMS:
Your server may have experienced this file system inconsistency problem if the
server is running VINES 4.10 (0) or 4.10 (1) and you see any of the following
messages or symptoms:
■ For non-Banyan, PC-based servers, the following message is displayed
on the server console screen or in the Server Operating System log file:
Bad block on hard disk device n, drive n
For Banyan/CNS and Banyan/CNS486 servers, one of the following messages
is displayed on the server console screen or in the Server Operating
System log file:
Bad block on System Disk
Bad block on /diskn
In the second message, "n" designates the affected disk, for example,
disk2.
■ Messages in the following formats appear in the File System Log section
of your server System Log file.
BAD BLKS I=nnnn
nnnnnn DUP I=nnnn
DUP/BAD I=nnnn
In these messages, the number of digits (n) varies from 1 to 10, as in
this example:
26077 DUP I=1543
DUP/BAD I=1668
■ You have data files that appear to be in an inconsistent state.
■ During a reboot, the server experiences an unusually long delay after
displaying the "Checking Disks" message. In this case, generate a log
file and examine it for the messages listed above.
Note that in all cases, examining your Server Operating System and System Log
files is highly recommended.
PREVENTATIVE MEASURES:
A site-specific patch (described below) is available to fix the problem. If
you have not obtained this patch and you are unsure whether your VINES 4.10 (0)
server has experienced this problem, you should take the following preventative
measures:
■ Do not overwrite any current system backups. If a data file on your
disk is inconsistent, you may be able to recover it from one of your
existing backups. In particular, do not overwrite any backup taken when
your server was running VINES 4.00, because your 4.10 backups may already
contain inconsistent data.
■ Downgrading your server to VINES 4.00 is a preventative measure.
If you are not running VINES 4.10 (0) but plan to do so in the future, you
should wait until you have the patch before upgrading or installing VINES
4.10 (0). It is imperative that you apply the patch with 4.10 (0).
SOLUTION:
A site-specific patch is available that fixes the problem for 4.10 servers.
The patch is shipped in two versions, named 4.10-CF-3 and 4.10-CG-3:
■ Use patch 4.10-CG-3 if you have patched your server with any of the
following patches: 4.10-AC-1, 4.10-AN-1, 4.10-AP-1, 4.10-BD-1,
4.10-BP-1, or 4.10-CB-1. Note that 4.10-CG-3 obsoletes these patches.
■ Use patch 4.10-CF-3 in all other cases. You can use this patch with
any other 4.10 patch, except for the patches listed above.
The problem fix will be incorporated in the VINES 4.10 (5) maintenance release.
When 4.10 (5) is available, use it instead of the 4.10-CF-3 or 4.10-CG-3 patch.
Note that the 4.10-CF-3 and 4.10-CG-3 patches are identical to the 4.10-CF-1
and 4.10-CG-1 patches, except that the -3 versions fix the CNS double-boot
problem, provide a more robust fsck (file system check) program, and display
shorter fsck messages for readability's sake. Note also that the -3 fsck
messages described in this bulletin are slightly different from previous fsck
messages that appeared in base 4.10 (0) logs or that are documented elsewhere.
If you applied either the 4.10-CF-1 or 4.10-CG-1 patch, you do not have to
apply the -3 version. (The -2 version was an interim version that was not
released.)
APPLYING THE PATCH:
The patch fix prevents future occurrences of the file system inconsistency
problem, but it does not recover from a previous occurrence of this problem.
Therefore, if your server has experienced this problem, use the following
recovery procedure to return the file system to a consistent state:
1. Manually copy any mission-critical file to a PC hard disk. Some files
may be only partially inconsistent and you may be able to recover a
portion of an affected file from the hard disk. The reason for copying
these important files is that if any of them are inconsistent, they will
be deleted from the system during the recovery process.
2. Shut down the server software from the server console and pick the
option, RETURN to Operator Menu.
3. Perform a full system backup and verify its readability. Do not
overwrite any previous backups you may have.
Be aware that the backup procedure may fail if it encounters
inconsistent files. In this case, continue with the procedure.
The inconsistent files will be deleted and will need to be restored
from copies on your PC (see step 1) or from a previous backup.
4. Restart services so that you can log in to patch the server.
5. Apply the 4.10-CF-3 or 4.10-CG-3 patch to your server. Both versions
of the patch will reboot the server.
6. Generate a System Log file (from a PC) or a Server Operating System
log file (from the server console). Be sure to save a copy of the log
file. See the following section for instructions on how to interpret
the messages in the log file.
The patch reboot forces the system to search the disks for inconsistent files.
Any files with inconsistencies that are found are deleted. To determine which
files have been deleted, examine the File System Log section of the log file.
If VINES internal files (such as the files for the SS or ST services) are
inconsistent or are deleted by the recovery procedure, the system will not
operate correctly. For example, you may not be able to restart services at
step 4 or the reboot procedure at step 5 may not finish properly. In this
case, you must replace the VINES internal files by performing a 4.10 upgrade
procedure. Be sure to reapply the 4.10-CF-3 or 4.10-CG-3 patch. See the
"VINES 4.10 Release Notice" for details on the upgrade procedure.
INTERPRETING THE FILE SYSTEM LOG SECTION:
At the end of the System Log file is the File System Log section. In this
section is a series of entries under the heading "fsck log." (When
generated from the server console, the log is called the Server Operating
System log and the final section is the File System Checker Log. There is
no "fsck log" heading.)
The following example illustrates a System Log file with these entries:
=============================================================
File System Log
=============================================================
===== fsck log ====
/dev/radusr
File System: disk1 Volume:
** Phase 1 - Check Blocks and Sizes
25111 DUP I=1541
BAD BLKS I=1541
BAD BLKS I=1543
24870 DUP I=1545
BAD BLKS I=1545
26077 DUP I=1668
** Phase 1b - Rescan For More DUPS
25111 DUP I=1492
24870 DUP I=1492
26077 DUP I=1543
** Phase 2 - Check Pathnames
DUP/BAD I=1492
FILE=/banyan/st/st
REMOVE? yes
DUP/BAD I=1541
FILE=/BFS/fs1/TEST.1/ABC
REMOVE? yes
DUP/BAD I=1543
FILE=/BFS/fs1/TEST.2/DEF
REMOVE? yes
DUP/BAD I=1668
FILE=/BFS/fs1/TEST.3/GHI
REMOVE? yes
DUP/BAD I=1545
FILE=/BFS/fs1/TEST.4/JKL
REMOVE? yes
** Phase 3 - Check Connectivity
** Phase 4 - Check Reference Counts
UNREF FILE I=1412 (EMPTY) Cleared
UNREF FILE I=1417 (EMPTY) Cleared
UNREF FILE I=1418 (EMPTY) Cleared
UNREF FILE I=1420 (EMPTY) Cleared
BAD/DUP FILE I=1492 (NOT EMPTY)
CLEAR? yes
FREE INODE COUNT WRONG IN SUPERBLK
FIXED
** Phase 5 - Building Bit Map 11204 files 139086 blocks 97920 free
*** FILE SYSTEM WAS MODIFIED ***
The fsck program makes a five-phase pass on each disk to verify and fix the
file system. Therefore, the log should report a series of five-phase messages
for each disk on the server.
To determine which files have been deleted by the fsck program, look for the
FILE= entry in the "** Phase 2 - Check Pathnames" section. In the example
above, the files named /banyan/st/st and /BFS/fs1/TEST.1/ABC were two of the
five files that were found to be inconsistent and were deleted.
Note that the "** Phase 4 - Check Reference Counts" section may contain a
number of entires that are either redundant or unrelated to the file system
inconsistency problem. These message include UNREF FILE, BAD/DUP FILE
I=nnnn, and FREE INODE COUNT WRONG IN SUPERBLK. You can ignore
these entries.
The types of deleted files and the recovery procedure that you should follow
are as follows:
■ Files whose pathnames begin with "/banyan" are VINES internal files,
and in most cases are necessary for the system to operate properly.
To recover these files, you must perform an upgrade procedure.
■ Files whose pathnames begin with "/BFS/VINESFiles" are VINES FILES on
drive Z. To recover these files, you can restore them from backup media
or choose "Reload VINES Files from Release Media" at the Backup/Restore
menu. You can also recover them by upgrading the server.
■ Files whose pathnames begin with "/local" are Applications Toolkit files
or third-party files. To recover these files, re-install the Toolkit or
the third-party application.
■ All other files should be user data files. To recover these files,
restore them from copies on your PC (see step 1 in the previous section)
or from a previous backup.
Please note that the log file may contain these messages for any of the disks:
■ A message that contains the text: DUP TABLE OVERFLOW
■ A message that contains the text: ROOT INODE
If you see either of these messages, the affected disk may need to be
reformatted. In this case, contact your Banyan service representative for
assistance.
POST-RECOVERY RECOMMENDATIONS:
The 4.10-CF-3 and 4.10-CG-3 patches, as well as the 4.10 (5) maintenance
release, will prevent a reoccurrence of the file system inconsistency problem.
After you apply the fix, it is recommended that you take these two actions:
■ The fsck program verifies only the consistency of a disk's file system
structure. It does not verify the integrity of the data contained in
user files on that disk. Therefore, if you have any data verification
programs, you should run them on your data files.
■ Permanently archive your final 4.00 backup and the 4.10 backup that
you took before applying the patch.
If you need assistance at any time, contact your service representative.
Banyan will verify your findings and provide guidance in the recovery procedure.