RE: RMAN backups
- To: <rgramolini@xxxxxxxxxxxxxxx>, <jrsmiley@xxxxxxxxx>, <richard.ignizio@xxxxxxxxxx>
- Date: Tue, 21 Jun 2005 10:43:59 -0700
I think the results I have shown below, although accurate, may be misleading.
After further analysis I noticed that when we first implemented incrementals,
the backup time was not much shorter than for the full backups, however
something changed in January that made the backup time for the Full backups
rise sharply, while incrementals remained consistent. I'm working with my tape
library admins to see what may be the cause and will reply later with my
findings. In the mean time, please do not expect your backup time to be
dramatically reduced by implementing incrementals like I have shown below - I
believe there is some other force at work here besides just the incremental vs.
full difference. It may be something simple like the tape library is busy with
replication on Thursdays when we run our Full backups or something like that.
Regards,
Brandon
-----Original Message-----
From: Allen, Brandon
Sent: Tuesday, June 21, 2005 10:17 AM
To: 'rgramolini@xxxxxxxxxxxxxxx'; jrsmiley@xxxxxxxxx;
richard.ignizio@xxxxxxxxxx
Cc: oracle-l@xxxxxxxxxxxxx
Subject: RE: RMAN backups
We do save a significant amount of time and space by using incremental backups:
SQL>select avg(elapsed_seconds)/60/60 from rc_backup_set where db_key=2300 and
backup_type='D' and completion_time >= sysdate -45;
AVG(ELAPSED_SECONDS)/60/60
--------------------------
3.8742284
SQL>select avg(elapsed_seconds)/60/60 from rc_backup_set where db_key=2300 and
backup_type='I' and completion_time >= sysdate -45;
AVG(ELAPSED_SECONDS)/60/60
--------------------------
1.13801519
Regards,
Brandon
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]On
Behalf Of Ruth Gramolini
Sent: Tuesday, June 21, 2005 10:05 AM
To: jrsmiley@xxxxxxxxx; richard.ignizio@xxxxxxxxxx
Cc: oracle-l@xxxxxxxxxxxxx
Subject: RE: RMAN backups
John,
Unless something has changed with 10g, and incremental backup doesn't actually
save much time. Rman still has to read the block headers to see if the block
needs to be backed up. It mostly saves space on disc if backing up to disk.
Correct me if I am wrong!
Ruth
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]On
Behalf Of John Smiley
Sent: Saturday, June 18, 2005 11:19 AM
To: richard.ignizio@xxxxxxxxxx
Cc: oracle-l@xxxxxxxxxxxxx
Subject: Re: RMAN backups
Backup times with RMAN are going to vary greatly depending upon the hardware
and how many blocks need to be backed up. Even a very large database can be
backed up incrementally if very few blocks have changed since the last backup
with RMAN.
What might be a better yardstick is backup rate. The fastest RMAN backup rate
I've seen was published by Amazon a few years back. They attained 2TB / hour.
John Smiley
Technical Management Consultant
TUSC, Inc.
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