Using Oracle with CTE-U

When guarding an ASM disk with CipherTrust Transparent Encryption UserSpace, there can be a 10% drop in database performance. This occurs when the underlying device is in Oracle direct mode. This mode avoids double-caching, which consumes memory, and therefore impacts performance on some workloads.

This issue is affected by the block_o_direct parameter. If that parameter is set to 0, the IO will be reported as complete, (meaning committed to disk) before it actually is. This is a data integrity risk for a database, because the normal mode is to mark as journal complete as soon as the data is safe on a disk. This incorrect reporting could result in a race that could lead to a journal being cleared before the data is on the disk. If a crash occurs during this window, the data would be lost.

In this scenario, data integrity and performance are at odds. You must choose which one to highlight.

1. To set CTE-U for optimal data integrity, type the following command:

   voradmin secfs config block_o_direct 1
   

2. To set CTE-U for optimal performance, type the following command:

   voradmin secfs config block_o_direct 0