Re: tar program not suitable for backup?
Date: 1996/02/02
Message-ID: <W4FjPCAatVExEwtq_at_shimmer.demon.co.uk>#1/1
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>
>
>
The same problem can occur on AIX when using the backup command (which utilises tar). If you're not carefull and don't eliminate the sparse files, the database files will expand dynamically causing performance problems. We use cpio to be safe, it's also better for recovering using pattern matching.
Clive Bostock
Senior Consulant
KPMG (Health Systems)
Received on Fri Feb 02 1996 - 00:00:00 CET