Backups

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Backups

T_SqueaKquel

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March 17, 2010 at 12:59 pm

#230970

There is a main process that inserts data to a database every 20 mins. In this case, what is the ideal transaction log backup strategy. Should it be every 30 mins or 15 mins? Also, we are going with a nightly full backup.
Thanks.

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SQLRNNR SSC Guru Points: 281334 More actions · Answer 1

The answer to that is it depends. How much other transaction volume do you experience?

Personally without more info, I would lean towards every 15 minutes.

Jason...AKA CirqueDeSQLeil
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TheRedneckDBA SSChampion Points: 14001 More actions · Answer 2

CirquedeSQLeil (3/17/2010)
The answer to that is it depends. How much other transaction volume do you experience?
Personally without more info, I would lean towards every 15 minutes.

Agreed. Way to little information provided to give a good answer.

How big is the database? What are requirements for max allowable data loss? How much storage space do you have available for backup storage?

Once you get all your requirements hashed out, your question will probably answer itself.

The Redneck DBA

SQLRNNR SSC Guru Points: 281334 More actions · Answer 3

Jason Shadonix (3/17/2010)
Once you get all your requirements hashed out, your question will probably answer itself.

Agreed

Jason...AKA CirqueDeSQLeil
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SQL RNNR
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T_SqueaKquel Mr or Mrs. 500 Points: 558 More actions · Answer 4

CirquedeSQLeil (3/17/2010)
The answer to that is it depends. How much other transaction volume do you experience?
Personally without more info, I would lean towards every 15 minutes.

Even I am tempted to a T-Log every 15 mins and the data loss allowed is 30 mins.

The database is not very big, with a size of 20 GB and 50 - 100MB data input per day.

What does the rule of thumb say, backup timing should be less than the allowed data loss time?? If the answer is yes, then I guess I figured the answer to my OP would be 'It depends' as anything from 10 to 30 mins for a T-Log would serve the purpose.

Thanks..

SQLRNNR SSC Guru Points: 281334 More actions · Answer 5

If you're allowed data loss is 30 minutes, then either amount of time would be fine.

With 15 minutes, less data loss = better. The backup time should be negligible and the amount of data being inserted is not much either.

Jason...AKA CirqueDeSQLeil
_______________________________________________
I have given a name to my pain...MCM SQL Server, MVP
SQL RNNR
Posting Performance Based Questions - Gail Shaw[/url]
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T_SqueaKquel Mr or Mrs. 500 Points: 558 More actions · Answer 6

CirquedeSQLeil (3/17/2010)
If you're allowed data loss is 30 minutes, then either amount of time would be fine.
With 15 minutes, less data loss = better. The backup time should be negligible and the amount of data being inserted is not much either.

Yeah, the backup time is negligible, but the amount of data being input varies from time to time. I will go with a 15 mins backup strategy.

T_SqueaKquel Mr or Mrs. 500 Points: 558 More actions · Answer 7

I have couple of questions now..

1. How much overhead would it add if I include a verify backup when finished, is there a way to test it out.

2. With a full backup daily, would I just Append the t-logs to the existing media set or overwrite all existing media sets?

Gail Shaw SSC Guru Points: 1004504 More actions · Answer 8

T_SqueaKquel (3/17/2010)
1. How much overhead would it add if I include a verify backup when finished, is there a way to test it out.

Put it this way. Would you rather find out that a backup is damaged and not usable at the time you take the backup, or when you need to restore using that backup?

2. With a full backup daily, would I just Append the t-logs to the existing media set or overwrite all existing media sets?

Neither. Each log backup to its own file.

Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
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Steve Jones - SSC Editor SSC Guru Points: 736212 More actions · Answer 9

There verify typically isn't much time added. Not sure how much, but you could easily test this on your system.

In terms of logs, I'm with Gail. Each log file to it's own, new file.

T_SqueaKquel Mr or Mrs. 500 Points: 558 More actions · Answer 10

GilaMonster (3/17/2010)
T_SqueaKquel (3/17/2010)
1. How much overhead would it add if I include a verify backup when finished, is there a way to test it out.
Put it this way. Would you rather find out that a backup is damaged and not usable at the time you take the backup, or when you need to restore using that backup?

I would want it to be checked while its being backed up. That's why I plan to do a checkdb before the full back runs, so that I may go back to the backup in case I need to do a restore and be sure that my backup is valid and corruption free. So, now I will include this step for the t-logs too.

Thanks.

Gail Shaw SSC Guru Points: 1004504 More actions · Answer 11

No, you don't want to run a checkDB every time you back the log up. That's just insane. If you're backing up every 15 min, CheckDB can easily take longer than the interval between the backups.

Besides, in full recovery, corruption in the data file can't get into the log backups.

A database can be fine and the backup taken of it unusable. It happens, it means the backup itself was damaged or not written properly. That's why you should backup with the checksum option and do restore verifyonly after doing the backup to verify that nothing went wrong during the backup.

Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
We stand on the bridge and no one may pass

T_SqueaKquel Mr or Mrs. 500 Points: 558 More actions · Answer 12

GilaMonster (3/17/2010)
No, you don't want to run a checkDB every time you back the log up. That's just insane. If you're backing up every 15 min, CheckDB can easily take longer than the interval between the backups.
Besides, in full recovery, corruption in the data file can't get into the log backups.

Oh yeah, I was only gonna run the checkDB before the nightly full backup.

A database can be fine and the backup taken of it unusable. It happens, it means the backup itself was damaged or not written properly. That's why you should backup with the checksum option and do restore verifyonly after doing the backup to verify that nothing went wrong during the backup.

This means for my t-logs, I do a (i) Verify when finished

(ii) Checksum before writing to media

Thanks again.....

Gail Shaw SSC Guru Points: 1004504 More actions · Answer 13

T_SqueaKquel (3/17/2010)
(ii) Checksum before writing to media

No. Backup with the CHECKSUM option.

And both are for full and log backups, not just log

Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
We stand on the bridge and no one may pass

T_SqueaKquel Mr or Mrs. 500 Points: 558 More actions · Answer 14

T_SqueaKquel

Mr or Mrs. 500

Points: 558

March 18, 2010 at 7:42 am

#1135948

Thanks for the suggestions Gail...