Yes, a really nice new shiny feature where we have the ability to suspend and resume the encryption scan for TDE – Transparent Data Encryption which is available in SQL Server 2019. (Tested against the latest version CTP 2.4)
A really quick one today, something that made me think for a minute and I thought it might make others think too. So you have enabled TDE – Transparent Data Encryption (you can see these previous posts here: https://blobeater.blog/?s=tde&submit=Search) on your SQL Server database and in the back of your mind you know TempDB gets encrypted too.
TDE (Transparent Data Encryption) encrypts the data files at rest but don’t forget that it also encrypts your backup file too. I fancied looking inside a backup of my database before enabling TDE and comparing it to when enabled.
Working with a couple of databases that needed TDE I noticed when I enabled one of them that it was stuck on “encryption in progress” for quite a while.
I noticed that my backup was taking longer than usual.
I went to Perfmon to look at some counters, more specifically Physical disk:Avg sec/read(orange/yellow line) and Physical disk:Avg sec/write(blue line), yes it was very busy, much busier than normal.
Waits stats was painting the following picture: I was very intrigued with the sleep_bpool_flush so I headed straight over to the waits library.
You get this wait type when the checkpoint process realizes that it’s saturating the I/O subsystem. (https://www.sqlskills.com/help/waits/sleep_bpool_flush/), so it seemed that my backup could not even issue a checkpoint successfully. With that thinking I decided to do a manual checkpoint which just made the problem worse.
After some detective work I found the answer. Someone enabled TDE and it was going though the encryption process whilst I was trying to take a backup so my backup was never going to complete anytime soon.
The error message I was ended up with was “Msg 5901, Level 16, State 1, Line 7 One or more recovery units belonging to database ‘NEWdb’ failed to generate a checkpoint”.
You can use the following query to understand the state of the encryption process for your databases.
SELECT db.name,db.is_encrypted,dm.encryption_state,dm.percent_complete,dm.key_algorithm,dm.key_length FROM sys.databases db LEFT OUTER JOIN sys.dm_database_encryption_keys dm ON db.database_id = dm.database_id
When you have a state of 2 it means encryption is in progress, you may have heard of this as an encryption scan.
This behaviour is confirmed via Books on line and totally makes sense. (Last bullet point)
The following operations are not allowed during the CREATE DATABASE ENCRYPTION KEY, ALTER DATABASE ENCRYPTION KEY, DROP DATABASE ENCRYPTION KEY, or ALTER DATABASE…SET ENCRYPTION statements.
You live and learn.
All About Tech 