Failed Hotfix - One Or More Files Do Not Match The Primary File Of The Database

I've just applied CU7 to a set of SQL2005 SP2 servers with no problems, except on one server.
I've now fixed the problem, but couldn't find description of it elsewhere so post it here in case it helps anyone else with the same problem.


Here's the problem I had. The server is Windows 2003 with two instances of SQL 2005 SP2 (9.00.3186)
1) Ran the patch (SQLServer2005-KB949095-x86-ENU.exe)
2) C: drive ran out of space whilst patch was running against instance A
3) Cleared down space on C: drive
4) Patch had hung, after 45 minutes of no activity I killed it
5) Re-ran patch, it reported instance A as upgraded already and just upgraded instance B
6) After reboot instance A failed to start. Instance B started with no problem.

The service was failing to start with the following recorded in the log:
Server Microsoft SQL Server 2005 - 9.00.3239.00 (Intel X86)
[��]
spid5s The resource database build version is 9.00.3186. This is an informational message only. No user action is required.
spid5s Error: 5173, Severity: 16, State: 1.
spid5s One or more files do not match the primary file of the database. If you are attempting to attach a database, retry the operation with the correct files. If this is an existing database, the file may be corrupted and should be restored from a backup.
spid5s Error: 5173, Severity: 16, State: 1.
spid5s One or more files do not match the primary file of the database. If you are attempting to attach a database, retry the operation with the correct files. If this is an existing database, the file may be corrupted and should be restored from a backup.
spid5s Log file 'C:Program FilesMicrosoft SQL ServerMSSQL.2MSSQLDATAmssqlsystemresource.ldf' does not match the primary file. It may be from a different database or the log may have been rebuilt previously.
spid5s The log cannot be rebuilt when the primary file is read-only.
spid5s Error: 945, Severity: 14, State: 2.
spid5s Database 'mssqlsystemresource' cannot be opened due to inaccessible files or insufficient memory or disk space. See the SQL Server errorlog for details.



I think that the patch must have got part-way through instance A, enough to mark it as being patched, but not far enough to patch the mssqlsystemresource system database (note the version numbers in the log above - 9.00.3239 vs 9.00.3186).
The hotfix log records an error opening the registry, but the detailed log was overwritten by the subsequent (successful) run of the hotfix so there��s no more detail available.

To fix this I copied in the mssqlsystemresource mdf and ldf files from instance B (which wasn��t patched the first time round, and was subsequently patched successfully). From what I understand mssqlsystemresource is read-only and holds copies of system sprocs etc, so a copy will suffice. Plus I am assuming the SQL Server is clever enough to complain if it��s not happy with the instance of the file.

Note that the problem recorded elsewhere for this error, where mssqlsystemresource or other system DBs have been moved from their original installation folders, was not the cause here.
Not sure if this is the 'correct' fix, but it got Instance A up and running. Obviously YMMV