February 23, 2016 at 4:03 am
Hi Experts,
We have a 2 node Active-Active Cluster with 3 instances. The nodes are across 2 Data centers, data gets replicated using VPLEX. Now my question is when there is a corrupted DB in DC1, will the VPLEX carry over the corruption to DC2?
Will replication or Logshipping will help me recover database without corruption in case of DR? Logshipping is basically backup\restore so if i am not wrong this will carry over the corruption to secondary as well?
February 23, 2016 at 5:50 am
VPlex I believe copies stuff at the page level? If so, yeah, it's likely to replicate corruption.
Log shipping (or, since we're in the 2014 group, Availability Groups, a much better technology) is highly unlikely to cause corruption to be moved. A transaction doesn't corrupt the database. It's usually something within the I/O system that causes bad writes. This is not replicated through the transaction.
"The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood"
- Theodore Roosevelt
Author of:
SQL Server Execution Plans
SQL Server Query Performance Tuning
February 23, 2016 at 10:14 am
Grant Fritchey (2/23/2016)
VPlex I believe copies stuff at the page level? If so, yeah, it's likely to replicate corruption.Log shipping (or, since we're in the 2014 group, Availability Groups, a much better technology) is highly unlikely to cause corruption to be moved. A transaction doesn't corrupt the database. It's usually something within the I/O system that causes bad writes. This is not replicated through the transaction.
Thanks Grant.
We had situation when were we had corrupted DB in Prod which we realised only when we restored the bacckup in dev and then we run a CHECK DB there. so i was under the impression that backups carry those corruption forward. Again Logshipping is transaction log backup and replication is done by transactions . Please correct me if I am wrong.
February 23, 2016 at 10:58 am
Transactions and transaction playback, log shipping, are not the same as a backup, a page-by-page copy of the database. The processes of restore are different. The at rest copy of your database, the *.mdf file, was corrupted, so a copy of that database would include the corrupted pages. Does that seem clear?
"The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood"
- Theodore Roosevelt
Author of:
SQL Server Execution Plans
SQL Server Query Performance Tuning
February 23, 2016 at 11:01 pm
Grant Fritchey (2/23/2016)
Transactions and transaction playback, log shipping, are not the same as a backup, a page-by-page copy of the database. The processes of restore are different. The at rest copy of your database, the *.mdf file, was corrupted, so a copy of that database would include the corrupted pages. Does that seem clear?
Thanks Grant .
What i understood is logshipping or replication which is basically transaction log backup and transaction will not migrate the corruption . But a full backup does because it copied the entire DB which include the corrupt pages as well. Am I correct?
February 24, 2016 at 3:53 am
Yeah, that's pretty much it.
"The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood"
- Theodore Roosevelt
Author of:
SQL Server Execution Plans
SQL Server Query Performance Tuning
February 25, 2016 at 4:08 am
Grant Fritchey (2/24/2016)
Yeah, that's pretty much it.
Thanks Grant.
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