Re: tar program not suitable for backup?

In article <4e47vv$lok_at_raffles.technet.sg>, Ngo Lip Wee <lwngo_at_tmi.com.sg> writes
>Hi!
>
>I am using Digital Unix 3.0 and Oracle 7.1.3. I was told that
>the tar program is not suitable for database backup, owing to
>the following scenario:
>
>Disk /u01 contains datafiles of a database summing up to 2.6G
>(there are no other files).
>
>du, df and ls commands show 2.6G occupied on that disk.
>
>After tar of all datafiles to tape, erasing them from the disk,
>and doing a full restore, the following is observed:
>
>du and ls shows 2.6G occupied, but
>df shows much less than 2.6G occupied,
>and the dba_data_files view shows 2.6G
>
>It seems that the tar program packs the datafiles (database
>files are sparse in our case) as reflected by df. The concern
>here is will the 'free space' as reported by df (they shouldn't
>be free, they should be reserved for future table expansions)
>be used for some other unrelated files, causing problems to my
>database later.
>
>Any comment or advice would be much appreciated.
>
>
>Regards,
>
>Ngo Lip Wee
>email: lwngo_at_tmi.com.sg>
>
>

This sounds bizarre. As far as I know, tar is just a backup program and performs no compression or packing, so it should restore everything just right. There are one or two things that might go wrong with differences between the block size you wrote to tape, and the block size you extracted it with. What we use is cpio (especially for raw partitions). I'll follow this with interest. BTW, Oracle have said to us that they will under no circumstances support any database which you use compression tools on (in backups or elsewhere)...

-- 
Tom Cooke