On Mon, Nov 22, 2010 at 7:43 AM, Binand Sethumadhavan <binand(a)gmail.com> wrote:
2010/11/22 Kshitiz <kshitij_kotak(a)hotmail.com>om>:
I feel a full backup once in 400 days, with
hourly incremental, daily incremental and weekly incremental backup being rotated in a way
in which 1 full backup followed by 24 hourly incremental backups, interspersed with 7
daily incremental backups and 5 weekly incremental backups may be protection enough for my
data. What is the you all's expert opinion?
I am assuming you meant 40 days, and not 400 days. :-)
Let us say a full backup takes 30 minutes to restore, each weekly
incremental takes 5 minutes to apply and each daily incremental, 1
minute. Let us further say you have an outage 33 days after your
previous full backup. Now, the time for you to restore is:
30 minutes to restore the last full backup
4 x 5 = 20 minutes to apply the 4 weekly incrementals since the last full backup
5 x 1 = 5 minutes to apply the 5 daily incrementals since the last
Total time taken to restore = 55 minutes ~= 1 hour.
I feel we can provide better insight if he lets us know what exactly
he is trying to backup. Since he is using rsync, I assume he is
backing up files at the OS level. Now, what application does he use,
and how often to files get generated/modified at the OS level? That
would decide the frequency of his full and incremental backups.
If we are taking about OLTP here, then logic says the data be stored
in a database, not at the OS level. In such a case, the db will take
care of mttr, etc. The 55 minutes of data loss would be taken care of
by the redo logs (if Oracle).
I have never come across a situation where I had to run hourly
incremental backups at the OS level.