Why is my SQL Server Differential backup failing sometimes?

Question

I'm having an issue that only happens sometimes where my SQL Server differential backup job fails with an error message similar to

Msg 3035, Sev 16, State 1, Line 1 : Cannot perform a differential backup for database "MyDatabaseName", because a current database backup does not exist. Perform a full database backup by reissuing BACKUP DATABASE, omitting the WITH DIFFERENTIAL option. [SQLSTATE 42000]
Msg 3013, Sev 16, State 1, Line 1 : BACKUP DATABASE is terminating abnormally. [SQLSTATE 42000]

I'm currently using Ola Hallengren's SQL Server Mantenance Solution script for backup's, integrity check's and index maintenance. I've scheduled the backup job's as such:

• Full Backup of system databases every day @ 1:30 AM
• Full Backup of all user databases every week on Monday, Wednesday & Friday @ 2:30 AM
• Differential Backup of all user databases every week on Sunday, Tuesday, Thursday & Saturday @ 2:30 AM
• Transaction Log backup or all user databases every 30 minutes

I've also set the cleanup time to 168 hours...which is 7 days.

I know that usually when this error message comes up, it is due to a full backup not being present, or possible the recovery mode on a database being changed. I have checked both of these and neither seems to be the case. I can confirm that my Friday full backup was successful, however my Saturday and Sunday Differentials failed. There have also been no changes to the recovery model, and no manual backup taken through SQL Server.

It's worth noting that this only happens sometimes. Sometimes the differential backups work without a problem and other times they fail.

This server is a VM, and we are using VMWare vSphere/vCenter 6.5. I've talked to my server admin and asked how his backup is running an he told me that we are using Quest AppAssure which leverage VMWare snapshot technology, and that he is backuping the drives every x number of minutes, so it is possible that the time of his backup changes and eventually overlaps with mine.

We looked back at the time that his backups ran on the weekend and they happened within a few minutes before mine started. I'm wondering if this is causing my backup issues? if so is there a way to prevent this, or do we simply need to plan the backups at different times that don't overlap?

Thanks

Answer 1

Just wanted to post a update to this issue

We scheduled a call with Quest yesterday, and they assured me that their backup is only taking volume snapshots and will have no impact on my SQL backups. They said that the reason that i was seeing these errors is likely do to Rapid Recovery(I guess AppAssure was renamed to Rapid Recovery) and my SQL backup jobs both trying to use the volume shadow copy service at the same time and so we simply needed to stagger the backup jobs. I end up finding out that this wasn't completely true because the Rapid Recovery backups were configured to truncate my SQL Logs. I also told the guy from rapid recovery that when i queried the msdb backupset table that i was seeing backup jobs listed that lined up with the times of the rapid recovery backup. Still he assured me that it would have zero impact on my backups.

I was still concerned that the Rapid Recovery backups might be impacting the chain of my backup files, so in our test environment i right clicked on one of our databases and clicked tasks > restore >database just to see the recovery history. I see a database backup listed as type Full (Copy Only) which coincides with the rapid recovery backup, then a number of my transaction log backups.

It would seem to me that Rapid Recovery is definitely impacting my SQL Backups.

One other thing to note that i just tried in out test environment. I did a few tests backups using Full's, Transaction Log, Differentials and Full (Copy Only) just to see how things showed up in the restore window in SQL Server Management Studio.

So i realized that in the default restore screen, it tries to recover to the nearest point in time using the least combination of various backup files. To go past the last full backup, I have to use the Timeline option.

• I could see the Full backup as the first item, and then the transaction logs backups.
• Once i do the Differential backup, i see the Full plus the differential, but no more transaction log backups.... which makes sense since it's trying to get the the closest time possible for the recovery.
• Next if i do another Transaction Log backup, I see the Full, Differential and the Transaction Log back

One thing that surprised me however is if i do a Full (Copy Only) followed by a transaction log backup, that i see these two item in the list of files for the recovery, yet if i do a differential after a Full (Copy Only) that it show me the last Full (non copy only), plus the differential. I expected that the backups would always be based off of the last full, both for transaction log and differential backups. I thought that the Copy Only backups would be ignored in the backup chain.

Next I decided to use the timeline restore feature and select a point in time during my tests where the Rapid Recovery backup wasn't part of the listed backups, and do a verify backup. As expected it was successful. After this i tried a restore to another point in time where the Rapid Recovery Full (Copy Only) backup was listed and the verify failed on the Full (Copy Only) backup file from rapid recovery, since it doesn't exist on the sql server.

Any recommendations on how to fix this? The point of the Rapid Recovery backup is supposed to be to backup the machine, in case we ever loose the server and have to restore the entire server, plus for it to pick up my sql server backups to keep for retention, since i only keep 7 days worth of backup on the server itself.

Answer 2

We had another call with Quest today and figured out a solution to the problem.

It would seem that when configuring the backup through Quest Rapid Recovery, you have the option to do Machine level backups or Volume level backup. When it's configured to do volume level backups you can choose for it to either do a block level backup which isn't SQL Server aware, or for it to do a backup that is SQL Server aware, which ends up using the volume shadow copy service and these backups show up as Full (Copy Only) backups in the SQL backup history...even though you can't restore them from SQL Server.

Rapid Recovery can only do backups on a schedule, plus has the option to Truncate Logs after the backup complete to avoid filling the log files, but can't do transaction log backups, so you loose the ability to do a more granular recovery down to the second like with the native SQL Timeline Recovery...Which is why we chose to use native SQL Server Backups.

So to fix the issue, you need to either do a machine level backup which has not SQL Server Awareness/integration. Or you can do a volume level backup, but disable the SQL Server Writer extension, and the truncate logs options to remove the integration.

We've run a bunch of tests, and from the point/time that this change was done, we only see SQL Server backups and no longer the Rapid Recovery backups in the SQL Server Backup history.

So now i am in talks with my server/backup admin see if we can do a machine level backup once a day, so that we can do a machine level restore in case of disaster, and also add a volume level backup of my Backup drive, so that he captures my backups more frequently during the day. I think once this is complete, we'll have the best of both backup solutions.

• Ability to do machine level restores (Rapid Recovery)
• Retention of SQL Server Backups (Rapid Recovery)
• Flexible point in time recovery (SQL Server)

Answer 3

You can check the error log file.

• Your job may be the victim of deadlock transactions.
• Backup file location may not have enough permission. So, you should check all the possible error log files.