Storage Administration - Oracle Exadata Recipes: A Problem-Solution Approach - page 291

■ Chapter 15 provides additional details and information about how to capture Smart Scan statistics and
measure Smart Scan behavior. please refer to recipes in Chapter 15 to learn more about this topic.

Note

How It Works
Each Exadata storage cell in the X2-2 and X2-8 configurations is installed with four 96 GB PCIe Sun Flash Accelerator
cards, primarily designed to provide flash storage for Exadata's Smart Flash Cache and Smart Flash Logging features.
Each PCI flash card is partitioned into four sections, as discussed in Recipe 1-1, and each of these four FDOMs is
presented as a cell disk; on a single storage server, you will see 16 cell disks of type FlashDisk .

■ the exadata X3-2 and X3-8 storage cells are configured with larger pCi flash cards, yielding significantly more
flash storage. to learn more about the hardware configuration of exadata's flash cards, please see recipes 1-1 and 1-6.
Chapter 18 also provides multiple recipes on the topics of Smart Flash Cache and Smart Flash Logging.

Note

Exadata DMAs typically will elect to use all of the flash disk capacity for Smart Flash Cache and Smart Flash
Logging, but you can choose to configure these flash cards for permanent database storage. This is achieved by
building flash-based grid disks upon the flash disks to expose the storage to Oracle ASM, along with creating Oracle
ASM disk groups on these flash-based grid disks.
Many Exadata DMAs entertain the idea of placing permanent storage on flash grid disks in order to improve
performance. Our advice is that you should have a very specific I/O-latency business problem before proceeding with
this decision because using flash storage for your database files reduces the capacity available for Smart Flash Cache.
Additionally, it is common for Exadata DMAs to consider placing online redo log files in flash grid disks to provide
better redo log writer write times. With the advent of Smart Flash Logging and some general understanding of the
DRAM cache on each SAS disk, we do not generally recommend this type of configuration.

■ recipe 18-7 discusses the topic of Smart Flash Logging in detail, along with the write-back versus
write-through design details with exadata storage.

Note