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We are attempting to use TDE with SQL Server 2016 to encrypt a large database. However, when the encryption gets to about 91% we receive a drive space error and the encryption fails. Being that TDE does not cause an increase in the database size, would someone be able to tell me why this is happening?

My only assumption is that a copy of the DB is being encrypted and then the non-encrypted version is being dropped as part of the process. Which means we need to ensure that we have enough available space on the drive to support two .mdf files for the single database. Any insight would be greatly appreciated.

marc_s
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R4Z0R53DG3
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  • Kick off the TDE operation and then watch the log space. If you fill up the log, the transaction will fail and rollback. If it is not a log failure, then increase the drive size. Space is cheap nowadays. – dfundako Nov 26 '18 at 21:23
  • The issue is the drive that holds the .mdf files is running out of space during the encryption process. The database is about 550GB and there is about 350GB of space left on the drive, during the encryption process, our monitor shows that they 350GB drops to 1MB and causes the operation to fail. The drive for the log files is not the issue. Hope that clarifies a little. – R4Z0R53DG3 Nov 26 '18 at 21:32
  • Also, I understand storage is inexpensive, but I would like to understand why the file space is growing when it shouldn't be. – R4Z0R53DG3 Nov 26 '18 at 21:46
  • So, do your DB still work after 91% encryption ? If it does, it properbly worked on a copy of the DB .. The size not increasing refers to the feature when being operational. – Ebbe M. Pedersen Nov 27 '18 at 09:00
  • The database is not functional after 91% encryption. We had to drop the database and restore from the snapshot taken before the encryption. I think we need to investigate a little further. I was able to process the encryption and decryption of the same database locally without any issues. I had way less space available and still no issues. There must be something else going on that we have been able to determine at this time. Thank you for you assistance. – R4Z0R53DG3 Nov 27 '18 at 14:59
  • SQL TDE is done on the page level, so part of the increased space is taken up with page mappings (which pages are encrypted and which are not) – Neil Weicher May 20 '19 at 18:18

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