There are many important things to consider when planning out your SQL Server backup and SQL Server recovery environments. We will introduce some of the common challenges in this presentation. Data change and file retention issues arise when using SQL Server differentiation.

1. SQL Server Backup and
Recovery Challenges
SQL Server DBA Professionals

2. Consider this…
There are many important things to consider
when planning out your SQL Server backup and
SQL Server recovery environments.
We will introduce some of the common
challenges here.
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3. Backup capabilities
Microsoft provides out-of-the-box backup
capabilities through the BACKUP command.
Integrated backups features are capable – but
limitations start to show up as SQL Server
environments grow in:
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Database size
The number of databases
The number of instances
Critical business dependency on SQL Server
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4. Differential backup
We tend to introduce SQL Server differential
backups as a form of deduplication.
Differential backups only back up the data that has
changed since the last full backup.
Isn’t this a no-brainer? If you have a 100 GB
database that you backed up on Sunday and only 1
GB has changed by Monday, why would you back
up the 99 GBs of data that have not changed?
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5. Differential backup
Unfortunately, those who have worked with
differential backups have probably realized that
they come with some fairly significant challenges:
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Restores are always reliant on having access to the
full backup.
Restore time objectives are affected by the amount
of data change.
File retention is much more difficult.
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6. Full backup
Let’s review the “full backup on Sunday” example –
You do a full backup on Sunday and perform
differential backups throughout the rest of the
week.
If it’s Thursday and something happened to your
full backup, all of the SQL Server differential
backups you’ve created since are no good to you.
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7. Full backup
There is nothing that you can do with a SQL Server
differential backup without its associated full.
This can arise because:
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Someone has deleted the full backup, either by
mistake or by misunderstanding the importance of
the data.
Backup files were moved to hard-to-access
servers or other media offsite – meaning it can take
days before you can access it.
The file has been overwritten with another using
the same name.
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8. Full backup
It is easy to accidentally mess up your SQL Server
recovery by removing a full backup from the disk
without considering the interdependencies with
other backups.
Then there are the situations where the full SQL
Server backup is still available – you have been
careful about not deleting files – but corruption
strikes.
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9. Data change challenge
The effectiveness of differential backups is
dependent on the amount of data that’s happened
inside the database.
Let’s consider our full 100 GB backup on Sunday –
Your database changes at about 1 GB per day, so
your differentials will be 1 GB Monday, 1 GB Tuesday,
etc.
So differential backups make sense, right?
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10. Data change challenge
But what happens if you have a lot of data change
or an index of defrag/rebuild on Wednesday?
You may find that 80% or more of the backup has
changed, meaning 80+ GBs need to be backed up.
Now you have a differential backup that will
negatively affect, and nearly double, your SQL
Server recovery time.
Dell’s LiteSpeed for SQL Server offers rapid, effective database backup and recovery.
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11. File retention challenge
File retention is the automated process of deleting
backups from disk that are no longer needed while
also making sure that needed backups stay around.
Most retention routines simply remove backups
older than the specified retention period.
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12. File retention challenge
Let’s go back to our full backup on Sunday
example:
Suppose a DBA sets up their file retention to be five
day’s worth of backups, and a full backup is done
on Sunday, this could cause the Friday retention
routine to delete the full backup from 6 days ago,
leaving you with 5 days of worthless differentials.
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13. File retention challenge
A failed backup also fits into this category – a
second full backup fails for some reason.
Ideally, you would be notified of the failure and
possibly generate another full backup. But what if
you don’t catch it in time and Monday’s differential
backup now points all the way back to a full backup
from a previous Sunday?
If your retention doesn’t take this into account, you
run the risk of deleting a full backup that leaves you
in a unrecoverable situation.
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14. Learn More
To prevent downtime, click and download a Free
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Click to learn more about SQL Server Backup and
Recovery.
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