[Coreutils-users] Re: [Ocfs-users] From OCFS to tape via tar (and back again)

[Sunil Mushran]

not sure about sunspots, but as long as you do...
sync; sync; sync;
after tar -x, you should be fine.

bottomline, you have to flush the cache to disk.

considering o_direct is working during backups (does not work only
during restore), I see no problems with parallel backups... as in from
the filesystem point of view.

On Fri, 2004-09-03 at 15:06, Sheridan, Matt wrote:
> We're using RMAN to back up our 9.2 RAC database to an OCFS v1 volume.
> We have an existing shell script that we use for copying files from
> disk to tape via tar, one file at a time. (Don't ask why. It's a
> legacy script. Long story.) We're tweaking this script to use
> --o_direct when tarring the file to tape and that seems to be working
> fine:
>  
> # tape device is /dev/nst0
> $ tar --o_direct -cvf /dev/nst0 /ocfs/RMAN_test_file 
> ./RMAN_test_file
>  
> But, to pull that same file back off tape and save it to the original
> OCFS location, it seems that we cannot use --o_direct:
>  
> # skipping commands to reset the tape pointer to the proper location
> $ tar --o_direct -xvf /dev/nst0
> tar: /dev/nst0: Cannot open: Bad file descriptor
> tar: Error is not recoverable: exiting now
>  
> But, without --o_direct, it works fine:
>  
> # skipping commands to reset the tape pointer to the proper location
> $ tar -xvf /dev/nst0
> ./RMAN_test_file
>  
> We're assuming that using the above method (--o_direct when reading
> from OCFS and writing to tape, no --o_direct when reading from tape
> and writing to OCFS) provides us with a proper, working file that RMAN
> could use for restores. 
>  
> Is this assumption correct? Or, is there some issue that may bite us
> later? Like something related to direct I/O, stale cache buffers,
> incorrect byte-alignment, sunspots, whatever.
>  
> P.S. Our RMAN backups are happening purely on one node of the cluster,
> though the OCFS volume we're writing to will be mounted by the other
> nodes. We may decide at some point in the future to try backing up
> from multiple nodes simultaneously, but for now we're keeping it
> simple. Would backing up from multiple nodes simultaneously change the
> answer to the above question?
>  
> For the record, we're using the following:
>       * Red Hat Enterprise Linux Advanced Server 3.0 Taroon Update 2
>         (kernel 2.4.21-15.ELsmp)
>       * Oracle Enterprise Edition 9.2.0.5
>       * ocfs-2.4.21-EL-smp-1.0.13-1
>       * ocfs-support-1.1.2-1
>       * ocfs-tools-1.1.2-1
>       * coreutils-4.5.3-35
>       * tar-1.13.25-16
> Thanks in advance,
> Matt
> 
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